273 for early A

IMO, the factory had a good idea when they put solid lifters in the 273.
And if I was to build a 318 or smaller, because of the difficulty of making cheap compression, I would for sure use a fast-rate, solid lifter, cam.
Swept volume,if you don't know, is just the volume of one cylinder, that the piston sweeps thru on it's way from the bottom of the cylinder to the top.
A 360 has ~752cc,
a 340 has ~696,
a 318 has ~652,
a 273 has ~559.
AS you can see from 318 to 360 the increases are in about 50cc steps. But from 318 to 273 is a rather large step of nearly double that. This is what makes building a 273 so challenging.
The 360 has a generous amount of swept, and let's you be pretty sloppy with component selection, and still have a pretty good streeter.
How is swept important?
Well, it is the principal player in making cylinder pressure, that makes the heat, that drives the piston down, to make the power. But there is a limit to how much pressure you can make on pumpgas before detonation kills your dreams.
So the more swept you have, the more power you can theoretically make within the constraint of the detonation limit of your fuel.
How is that important?
Well, we have a limited number of players in the compression business, namely total combustion chamber volume (TCV), and the intake closing angle (Ica) of your chosen cam.. With various component selection this TCV can be in the range of ~67cc to~97cc. So,depending on the components chosen, you can make or break your combo.
For instance, on a 318; with 652cc of swept, and a cam-dictated 9.5Scr, you have the target of 652/8.5=76.7cc, which looks like an easy target. But you have 4 ways to get there, namely; chamber volume,gasket,deck-clearance. and eyebrows. So if your flat-top pistons are .057 down in the hole, that chews up ~11.2cc right there, and the gasket will be ~8.8 for the good ones, and that leaves you with 56.7cc for the head, and until recently, for performance, this was tough (expensive) to achieve.
But now with a 360, with a swept of 752cc, to get 9.5Scr, the TCV increases to 752/8.5=88.5cc. Now with flat tops .012 in the hole, the head requirement becomes 72cc, and there are plenty of those out there.
As it happens, a 360 can be built to almost any street Scr relatively cheaply.
But, lets back up to the 273. For an Scr of 9.5, it's TCV comes to 559/8.5=65.8cc. The stock closed chamber heads are spec'ed to be 57 (I haven't measured any) and the .028 gasket comes in at 6.8cc, totaling 63.8..... which leaves just 2cc for deck clearance. This is no big deal for what Mopar built these engines to do, but the 57cc head is a low-performance offering and is gonna need a lot of work to find power with.(read expensive)
Whereas the 72cc heads are a good deal of the way there, and have been used to good results right the way the come from Mopar.(read cheap)
So while I have nothing against a 273, it is however, an expensive project to get power enough to locomote your typical non-early-A streeter,with any semblance of authority.
Now, lets get back to the ICA, Intake Closing Angle.
The pressure building event of your engine cannot start until the valves, specifically the intake valve is closed.Your cam manufacturer specifies (usually) the advertised duration of his cam. But the specified number is not the actual fully closed point, but rather some very small opening point that he considers closed enough. Some manufactures choose .008tappetlift, some .006 and others .004. The actual fully closed point can be 20 or 30 degrees further on down the road. This doesn't matter too much, because once the engine is running, it is small enough,time-wise, not to be a problem. So the spec'ed advertised numbers can be used to determine something called the Dynamic Compression Ratio (Dcr). This is a formula that uses the left-over stroke at the time of advertised closing, to calculate the theoretical compression ratio that the engine will be seeing, and more specifically what your chosen fuel will be seeing. If your fuel can only support a Dcr of 8/1 then you cannot build your engine to make 8.1 Dcr without risk of destroying it. This, going back to the 273, is, or can be, a real handicap for that displacement. Again, for a street 360, you can be pretty sloppy and still have a nice streeter.
In other words, Scr is a means to obtain the maximum Dcr with a chosen ICA, for to use a certain fuel.
So, to recap, the ICA is one of two major players in choosing an Scr for your build. The other is elevation. The Effective Compression Ratio (Ecr), namely the pressure your engine actually has to work with, varies with the air density, which varies principally with elevation; namely the higher you go the thinner or less dense the air becomes.This thinner air makes it more difficult to make power with, and so you have to build to a higher Scr, to re-establish your chosen pressure, that still allows you to run the chosen fuel.
So now you may be really confused.
What is Effective Compression Ratio (Ecr)?
At any given time your throttle valves can be between almost-closed and WOT, and your Rpm can be just about anywhere. Of course this means your engine could be inhaling a minimum amount of air to a maximum. Well at idle, your engine is gonna only be able to ingest a few molecules of air, and they are gonna expand in your cylinder to fill it, but the molecules are gonna be far apart.So up comes the piston and squeezes them all into the same old chamber. But instead of the pressure being 160psi, maybe it's only 80.. So if 160 makes 9.5Scr@sealevel, maybe 80 makes 50% of that or 4.75 Effective Compression Ratio.
And if you drive this car up to 5000ft, and the max-pressure drops to 150 WOT, your Ecr will drop,from the Scr of 9.5, which was 8.0DCr at sealevel, to a Dcr /Rcr of perhaps 7.5 ..This is serious business. So much so, that if you optimize your combo for 5000 ft, with best gas available, then you better be real careful descending to lower altitudes.You have to take altitude into account with every build.
But the question was, which cam.
I personally, would not run a 318 or smaller, with an HFT. The actual on-the-seat-and-closed point of the intake valve is an unknown,until you install the cam and measure it. And I don't like that unknown, because it is a known pressure bleeder,and I cannot compensate for it during the build. Yeah, I like to run on the upper edge for midgrade 89octane gas, so that if I screw up, I don't have a do-over, but if I don't screw up, I have a dynomite engine.
So in your case; it depends on how much money you are willing to spend, and how much band-aiding you are willing to do afterwards.
If you have a pile of parts you wanna use, then prep what you have, cuz it's cheap, then measure the players and compute the Scr. Let that dictate your ICA, and slip in whatever cam you have closest to that, and call it done. Then if the bottom end goes away just slap a hi-stall on it ( bandaid #1). And if she's slow to 60mph, just slap some 4.30s in the back, (bandaid #2). Those are the band-aids. Sometimes the band-aids cost more than just fixing the Scr and run the cam your combo demands.
My 318 combo, if I had to build one, would demand a fast-rate solid-lifter cam, for max duration at .050 which is the actual important power-producing number, while maintaining a high Dcr, so I can run 3.55s or less and still get a modicum of fuel economy, cuz............. when the combo is sharp, I just wanna drive it every where all the time.
If I had to pick from your three listed;
I would not use the 112LSa, unless I specifically wanted the small overlap spec.
That leaves the Whiplash 213/226, the Crane 216/216, and the Mopar 220/224.
For me the Crane Single pattern is out.
Between the Mopar and the Whiplash, it's kindof flip-a-coin, except; the Mopar is a full size bigger at peak power, while the whiplash is a full size bigger at the bottom....... if I estimated the advertised spec correctly. Since I cannot know that, I reject the Whiplash on the those grounds only.
That leaves you with the Mopar 220/224
but wait! Remember the Crane. It is spec'ed at .004 lift. If I estimate the duration down to say 266* for the same .008Tappet lift as the Mopar and Whiplash, Suddenly, in at 106*, it becomes practically the same as the Mopar but with 8* less overlap, so idles smoother, while sacrificing a few horsepower. Here is the comparison, with the Crane sized down to estimate the .008T-lift;
268/272/120/112/54overlap, in at 104, the Mopar
266/266/121/113/46overlap, in at 106, the Crane
As you can see, the Crane at 266 exhaust, is 6* less than the Mopar at 272, and the overlaps are 8* apart. But what you don't see is that at those installed angles, the effective overlaps are actually 38* for the Crane and 48* for the Mopar, so that is a lot smoother idle for the Crane... if that matters to you. The .050s tell the story tho, the Mopar intake is ~4* bigger, so, IDK ~5hp on that, and maybe ~10 on the overlap with headers, for a total of perhaps 15hp with headers/ 5 without, advantage to Mopar. The Icas are within 1* so the rest is a wash. So pick your poison as to smooth idle. Oh wait. the much less overlap of the Crane is also gonna contribute to better city fuel economy; gear for gear.. Now recall that I fudged the crane down to 266 from 272, in an effort to make it an apples to apples comparison.
As for me, it would be the Mopar, because it has some flexibility in the cam-timing that I might want to exploit, if I had the pressure to play with.The Crane has no such flexibility.
Just to throw more confusion at you
This Mopar cam may not seat the intake fully, no longer leaking,until something like~304* just like the Crane. It's really hard to measure the actual point. And this is why I would use a solid lifter, cuz when the lash is set, you know exactly when the valve is fully closed. That means you can calculate the exact Dcr. That means you can target the cylinder pressure pretty accurately. And that means you can build to 91 octane gas, which is about 5 psi higher, than 89. And that means more low-rpm torque, more midrange power, and better fuel-economy.
But further, solids can be designed with faster rates of lift than FTHs, cuz their lighter in weight and follow the lobes better; (well they used to). And that means for the same advertised spec, you might get the next bigger .050 spec. OR more importantly, for the same .050 spec, your intake valve will hit the seat ~3 or 4 degrees sooner on the advertised spec but perhaps 20/30 degrees sooner in real, actually-slammed-shut, no-longer-bleeding-pressure, degrees.
And one more benefit; if the intake is on the seat sooner, so is the exhaust, and that means more cooling time for it, reducing the risk of detonation. But now, knowing that, means you can mess with the overlap cycle and let the headers really earn their keep. Headers are so much more than just an escape route for the hot gasses.
I gotta quit, I'm supposed to be doing other stuff,lol.