Depending on hp output will help with core selection. If you are gona stay mostly stock,any core in GOOD SHAPE will do.I have built 2-1974 440's with 450-500hp,using cast crank,rebuit 452 heads,and yeah I beat the one in my car,not a problem so far.But my core was low miles and ran like a champ before rebuild just a stock smog 74.
From my understanding 68-75 are best,have heard about 76-78 "thin wall" and you are limited to .030 overbore,but can not comment from lack of dealing with block from this time frame.And if you are gona stay under 500hp then even the 76-78 should be fine.
I feel it all depends on what you want to do with it.