72 340 build vs...other options

If just going by blocks (bore size) since most parts are interchangeable, would make 340 1st choice, 360 2nd, 318 3rd and 273 4th, cause 340 are expensive and hard to come by 360 would be the general best choice and if sticking with stock strokes makes a better streetable choice but 340 block with a 360 stroke be better. If looking to build an engine that revs but don't have money for crazy heads, 273/318 would make a good higher rpm engines.

To me you should be asking how much power and where (rpm) that tells you cid that's needed for the job.