In terms of years of block for B/RB, agree they all can be good. Cylinder wall thickness, verified by sonic check, is a big variable for any block regardless of year manufactured. Also other details about block condition which a good machinist and engine assembler checks.

If you do not know this detail (with confidence) about the engine you are considering buying, buyer beware.

I run a '78 "smogger" block pretty hard and no issues (592 HP/687 ft lb). It checks out OK in wall thickness and other areas. Also the late 400's
had stronger main bearing support vs earlier blocks and in this respect were better.