It’s like NC said above. Low 12’s in a 3300 pound car takes about 375 honest horsepower to run low 12’s. You might not get the ET but the MPH should show enough to get a low 12 pass.
You already know this but with the bore limits it makes it that much harder for the same cylinder head to make power.
A 340 at 375 hp is 1.1029 hp/cid.
A 273 at 375 hp is 1.3736 hp/cid.
Two tenths of a point don’t sound like much but when you are bore limited it’s a bear to get it.
Doing the same math a 408 is .9191 hp/cid.
Even with a 4.56 gear and a 27 inch tall tire about 6500 rpm. For some guys that’s a deal breaker.