I sought out a 230 casting in that date range that most recommend - pre 10/71, and it sonic checked about the same as two later ones I've recently bought pretty cheap. From looking at the webbing of both types, I feel any 400 block will probably have similar life expectancy in a street/strip stroker like I'm planning.

If I was to step up the power a significant amount I'd definitely go with an aftermarket low deck block.