All I have to say is WOW.
No disrespect to the builder, but that block would have been in the scrap pile, late blocks (I'm not that old, but that's a late block IMHO) are so lightly cast, to get a good one, you need to buy three or four cores....Same goes for the heads.
I would look for a mid 70's core and have it magged and sonic checked before putting one milling tool to it.
Also, check for centered camshaft and main bearing holes, I once saw a Tonawonda 454 (1999) that had over 3/8" offset in the cam bore. Guess what that would do to everything else? The oil pan leaked from day one, the pan rail bolt holes actually protruded through into the crankcase

Hope you have better luck on the next one.

May get at least an hour out of it

GT