Gears are easier than an engine swap. Later 318 are very low performance engines. You are going from a 273 with over 200 hp to a 318 that might be 150 hp. Good luck.
As to gears; I absolutely agree with you. Swap in an 8.75 and start collecting pumpkins.
As to the engine comparison, IMO, that's not fair;
How can you argue with 16.6% more cubes.........
The 318 makes tons more torque at low rpm and if neither combo spins off the line; the 318 will be quicker to at least 3000 rpm, more like 3600. With 3.23 gears you could be looking at 27mph. With 2.76 gears, more like 32.
And this is exactly what the OP is looking for.
I can tell you that my winter-motor, back in the early 2000s, was an outstanding winter combo. That was a 1973 smog-era 318, with nothing but a 4-bbl, headers, some valve springs that let her buck, oh and dual full-length 3" pipes..
Some winters I ran an A998(2.74 low) with a 2800TC, and other winters I ran the Commando 3.09 low gear with a clutch.
The rear gear might have been anywhere from 2.76 to 4.30 depending on my mood, or if the GVod was also on there.
There is nothing slouchy about a 318 if you let it breath and rev it up. They get their slouchy reputation because they are usually saddled with ridiculously high starter gears,very-low stalls, and grossly retarded timing; which would only kill the Commando 273, even worse. After 3600 or so, that low-compression Scr is not a real big handicap.
If you already have a 318, any 318, then I vote using it, with a 4bbl on a smallport intake, and give her a low-restriction dual exhaust. If you can find some small-chamber heads, great! but that is not a big deal. Then lay a curve in the distributor and have at it.
For best results, absolutely for sure, treat her to some rear gears.
jus my opinion
