(Newbe) 273 to a 340 and tremec 5speed swap.

One of the things that makes a BB so attractive is the low-rpm torque.
But what you are actually feeling, once that engine is installed, is the combination of that engine-torque, multiplied by the gear-ratios in the transmission and in the the rearend.

What I mean is this;
say your 440 makes 440 footpounds at some very low rpm, and say your manual-transmission has a 2.66 low gear. and the rearend is a 2.94. Then, into the rear axles will go, up to;
440 x 2.66 x 2.94 = 3441 ftlbs which is a really big number. and everybody loves it. But it is so high, that flooring the gas pedal just kills the tires. A reasonably good number for 295 street tires is around 3000. which means that the 440 would be adequate with a 2.56 rear gear or with only 370 ftlbs, or like a single-barrel carb, lol.
By contrast; say you had a 318, putting out 318 ftlbs into that same trans but with the more popular 2.76 gears. Then
318 x 2.66 x 2.76 = 2334; so of course it feels a lil sucked out, cuz comparatively, it is. To get to 3000, the 318 would need to make;
3000/ (2.66low x 2.76grs) = 408 ftlbs, or
3000/ (2.66low x 318ftlbs) = 3.55 rear gears; Or
3000/ (3.09low x 318ftlbs) = 3.05 rear gears..

But say you had a 360, making 360ftlbs, into a 3.09 low gear with 4.30 gears, like I once had, lol; then
360 x 3.09 x 4.30 = 4783 ftlbs. This is 39% greater than the 4400. So not so sucked out now, is it!

But say Second gear in this trans is 1.92,
Then the 440 will be sitting at, up to
440 x 1.92 x 2.94 =2484ftlbs, compared to the 360 at
360 x 1.92 x 4.30 =2972, the 360 is still leading
And this will continue in every gear.
The downside is that, the hiway cruising-rpm; which for the 440 will be 65= 2380 versus the 360 at 3580. However, with a 5-speed/overdrive, this could be reduced to around 2540.
But because this 360combo has such a preponderance of torque multiplication, we could take out that super-low 3.09 trans and take out the 4.30s, in favor of the 2.66 gearset and 3.55s.
In first gear then, we would now have
360 x 2.66 x 3.55 = 3399, which compares well to 3441
of the 440. and in Second we would get
360 x 1.92 x 3.55= 2454, comparing well to the 440@ 2484
but in overdrive, we now get 65=2100.
So in every respect, as a city car, the 360 is feeling like a 440 with 2.94s.
But you say it's not fair to install 2.94s on the 440!
Well; look at the number, the street chassis cannot handle those numbers anyway and giving the 2.94s to the 440, gives it at least a fighting chance on the cruise rpm.
Either of these combo's will already smoke the tires at WOT all the way thru First gear, and probably to 50/55 mph in Second. And Either of these combos will pull a trailer. and Either of these combos will be a joy to drive around town.

But you ask, what about the 340?
Well same deal, except to match the 440/2.94s/Second gear, it will need 10% more rear gear, so 3.73s; for a first gear of
340 x 2.66 x 3.73 = 3373ftlbs. and a Second gear of
340 x 1.92 x 3.73 = 2552, Both of which compare well to the 440 and are more than adequate for to have fun with, in a street chassis, and finally; in overdrive, the cruise rpm is
65= 2200 purrrrrrrrrrfect
What the 5-speed does for the 340, means that you can take a lotta camshaft out of it. You can build it stock, or even with a smaller camshaft than stock, to pick up some mpgs at 65=2200rpm....... and still make the 440/2.94 numbers in First and Second

Having said that;
a 360 with a Mopar A833-overdrive is IMO the ideal combo for this simply because it is so cheap.
The trans has ratios of 3.09-1.67-1.00-.73od. To get the Second gear to match the 440, she would need ;
2484/(1.67 x 360) = 4.11s, for, 2470 ftlbs
First gear would then be up to;
360 x 3.09 x 4.11 = 4572, a ridiculously high number, and she cruises at 65= 2430
Case closed,
except for, I am talking about a stock 360 with a 4bbl. And, that combo of 1.67 x 4.11 will hit 65 @ 5555 rpm@ WOT, about perfect; so fourth being a stretch is not so big a deal. and since the numbers are so high, you could easily sacrifice some of that. My favorite for this combo would be 3.55s, for 65=2100, and
360 x 3.09 x 3.55 = 3950 which is more than enough for whatever street tires you install, and, Second gear is
360 x 1.67 x 3.55= 2134 ftlbs which is still 86% of the 440s 2484, and again, more than adequate.

I ran this combo( A833od/3.55s) for several years, and was pretty happy with it; allbeit, my 360 was a torque-monster.
In the end tho, with a bigger camshaft, having lost some bottom-end torque, I went with the Commando 3.09 low gearset/3.55s/and a GearVendors overdrive. It's been that way now since 2004.

BTW-1
I just gotta say, having spent two decades with a 360 on this last combo, for me the most important lesson I learned was that for me, the Roadgear of 6.82, was all that mattered; with cruise rpm a closer second. The engine doesn't care how you get that number. Any combination of trans gear times rear end, that got me at least close to there with my 360, was gonna be just fine. and so;
Rear gear time Trans gear;
3.55 x 1.92= 6.82 in Second
4.11 x 1.67= 6.86 ^
4.30 x 1.67= 7.18 ^
3.73 x 1.77= 6.60 ^
3.91 x 1.77= 6.92 ^
2.76 x 2.66= 7.34 in First
4.88 x 1.40= 6.83 in Third, yes I really tried it.

BTW-2
As to cruise rpm; If you have a factory Ignition Distributor, there is no good reason to cruise at under 2000, because it is impossible for this distributor to provide adequate spark advance. 2400 is a good place to be; 2200 if you're willing to work at it.
Without adequate ignition-advance, your fuel-economy cannot be optimized.

BTW-3
I'm just tryinta save you;
money, time, fabrication, and aggravation.

BTW-4
I think my favorite combo for this notchie, would be a
273-4bbl/T5 combo, which, if my notes are right, has ratios
of 3.83-2.33-1.44-1.00-.79od These gears offer very nice progressive splits, and are perfect for the 273.
With 3.55s this would give you;
273 x 3.55 x 3.83= 3712 in 1st, comparing to 3441/440,
273 x 3.55 x 2.33= 2258 in 2nd, comparing to 2484/440,
and 65= 2270, again, purrrrrfect


BTW-5
I have to say this for Rumble; else he jumps on me;
All numbers are WOT potentials, and apparently do not reflect the driving habits of most men. Which is why we all seem to build 400+hp engines...... or want to install strokers or 440s ............
Apparently I am a one of none, WOT throttle-stabber.