My requirements... what to build?

I have never heard anything about the 72 and earlier blocks being weaker. Anyone else have an opinion on that?

The only thing I can think of related to that is that 73 and earlier (or maybe it was the 72 and earlier) 318's had lighter connecting rods. The 318 production rods were changed to the heavier 340/360 rods in '73 or '74.

If you are changing rods anyway, then that is a not issue.

For stroker kits, look at SCAT and Eagle. The Eagle cast cranks seemed to have some issues at some point in time; not sure if that is still the case. So I'd personally look at SCAT cast crank kits, or forged crank kits from either.