Yet another 273 build advice thread!

IMO;yur on yur way to screwing up
Wrong combo of cam,crank,gear, and log manifolds
Not a fan of converting to hydraulic lifters.
Didn't get past post #1
Forget the 340 crank; it's balanced for heavy forged pistons and heavy rods. I will cost you a lotta time to get the weight down.
The 273 has just 559 cc of swept area,
This makes getting the compression up very difficult.
If you stick a big cam in there with low compression, it will be a dog with those gears, no matter how sweetly it idles. The hydraulic cam compounds this by virtue of nobody knows when the intake will finally be on the seat and not leaking. The 273 absolutely needs a solid lifter cam, to exactly control when the intake is closed.
here's what I'm talking about; the only thing I changed in the following examples,was the Scr (Static Compression Ratio)
Static compression ratio of 8:1.
with that 255/261 cam in at 107.5 for an ICA of 55*
Effective stroke is 2.76 inches.
Your dynamic compression ratio is 6.83:1 .
Your dynamic cranking pressure is .............................. 132.22 PSI.
V/P (Volume to Pressure Index) is .............................. 91 very doggie

Static compression ratio of 8.5:1.
Effective stroke is 2.76 inches.
Your dynamic compression ratio is 7.24:1 .
Your dynamic cranking pressure is .............................. 142.90 PSI.
V/P (Volume to Pressure Index) is................................. 98 less doggie

Static compression ratio of 9:1.
Effective stroke is 2.76 inches.
Your dynamic compression ratio is 7.66:1 .
Your dynamic cranking pressure is.............................. 153.97 PSI.
V/P (Volume to Pressure Index) is............................. 106 still doggie

Static compression ratio of 9.5:1.
Effective stroke is 2.76 inches.
Your dynamic compression ratio is 8.08:1 .
Your dynamic cranking pressure is ............................165.15 max PSI. for best pump gas
V/P (Volume to Pressure Index) is ............................113 the best it can be with this cam, in at 107.5.

ok so lets say yur gonna limit the pressure to 160 from now on to use say 91 gas in your application, here it is;

Static compression ratio of 9.3:1.
Effective stroke is 2.76 inches.
Your dynamic compression ratio is 7.91:1 .
Your dynamic cranking pressure is .......................160.61 PSI.
V/P (Volume to Pressure Index) is....................... 110 the best safe-pressure number
Ok so 9.3 is the target Scr... so 559/8.3= 67.3cc is your minimum total chamber size. How you gonna get that?

Ok now lets go down two cam sizes, and again limit the pressure to 160ish.

Static compression ratio of 8.9:1.
Effective stroke is 2.89 inches.
Your dynamic compression ratio is 7.89:1 .
Your dynamic cranking pressure is........................ 160.08 PSI.
V/P (Volume to Pressure Index) is .........................115 instant torque!
Your new minimum chamber size is 559/7.9=70.76cc. Now that is easily doable.

Now
none of these cams are gonna be fond of 2.76 gears. with the A998 and it's 2.74 low-gear being a starter gear of 7.56
But 3.23x2.74=8.85 is doable, with a good TC having an internal Multiplier of at least 1.6, to get an instantaneous zero-mph ratio of 14.2 decaying to 9.29 as the car gets moving.
Next
if you want to spin the tires yur gonna need about 200 ftlbs at the crank to get her started. 200 is a lot for a 273. Ima thinking a 2800TC will cover it
for the torque monster 2-sizes smaller cam, than the 255/261/110 you got yur eye on. Ok 200 x 14.2=2840 ftlbs to the road, and this decays to 200 x 9.29=1858ftlbs to the road, which is not wanting to spin much longer, but with a rise in rpm that 273 might just keep it going for a bit in yur lightweight chassis with it's small-tire restriction.
If you insist on that cam, yur gonna need more gear than 3.23 or more stall, or a supercharger.

Or you could switch to a solid lifter cam and shut that pesky intake valve sooner, while retaining the [email protected].
Course none of these combos are gonna like log exhaust manifolds, which will kill the overlap cycle, and it's attending horsepower bump, and the 214* cam will if yur not careful, suck gas.
It's just all wrong for your stated useage.

And the final insult
lets say you installed that 255/261/110 cam and 3.23 gears. Ok that cam is gonna power peak around 5000 or more with logs,or less depending on the heads and stuff, at....42 mph with that 2.74 low gear. But at low rpm , unless you dress it up with the 2800TC, it will be a lil doggie.................
Whereas the 2 size smaller combo will be a powerhouse down low with maybe a 2200 stall TC, while peaking something like 400 rpm sooner or at 38 mph, altho giving up some power.

So the question is; where do you want the power to be?
IMO, this is more important to your combo than how much power it makes or how lumpy it idles.

I got an idea; figure out the total chamber volume without any machining, besides the boring. Then lets work the formula backwards and fit the cam into that Scr for the available gas, and the application you stated. Just keep your eye out for pistons hitting things and the final Quench-distance will be very important.
You'll be targeting a total chamber volume between 67 and 71 cc.
I think, with a solid-lifter cam, we can find you something to work with whatever you come up with...... it ain't rocket-science,lol.