383 block strength?

100% correct. The part you are missing is the succession of those engines, related aftermarket parts and modern technology. For example, the Chevy small block started it's life at 265, then 283, 327, 350, 400 and now lives at 427 cubic inches in a block that will happily live at 1,000hp. Similar can be said for mopar.

Yeah I get it. I've always been a sucker for a stock stroke build. I love an underdog. I guess primarily because that's all I've ever really been able to afford. I've seen a few pretty gnarly 383s.