273ci thoughts?

Gears do level the playing field. In two gears at least.
But the smaller the engine, the smaller the field. And the faster you go, the more power yur gonna need.
Streeters have several targets on the field, such as;
Ability to take-off in a timely manner.
The zero to 60 mph contest
Passing power
Cruise rpm (NVH)
cruise economy
and my favorite, the jump at 32 mph.
The bigger the engine is, the more targets it can hit.
If you need Power WITH Economy something has to give. Forget the 440Magnum, and forget the mini-me.
If you need Power, Economy, AND torque, really, you only have one or two choices
And if Power, Torque, economy and Cost to build, then your are down to one choice. A large enough bore, a long stroke, good heads, a small or modest cam,and easy Scr target, and as little machining as possible.
Which SBM does all that for low dollars?

And one thing nobody mentions is weight.
Those early As have about a 12 to 14% weight advantage over a 67 to 72 Dart, and maybe 20% on a later Dart. The 2bbl 8/1-318s might be a slug in a 2.76 equipped 75 Swinger; but dress it up like a Commando and swap it into a lightweight-A, and "fast" will become fast-er. There's a reason the 273 stopped being used in 1969, and I submit that cars were becoming porkers, and the 273 just ran outta juice for 2.76s and the taller tires.

And face it; a 318 is just a big-bore 273.
And a 340 is just a big-bore 318, with added breathing
And a 360 is at it's heart,just a stroked 340.
I never ever heard anybody complain about how slow his 340 revved, with those pig-heavy forged pistons. I mean they are ~ 200 grams heavier than the 273's ! Mostly, the E-70/14s gave up right away, and then they just spun, and spun, and spun.