well if you wanna run 70-80 comfortably you might want a 350 with the camero rear end.. dont think a 230 would do the trick,, might for a while..
another deal is to remember these are old trucks any you better make sure they are in good shape to run that fast.........
by the way,, you wont need the powerglide.. just send it to me,,just kidding, those are prime things around here........good luck with your project,
welcome to the bolt.. got a good little 52 ready to roll for sale.. its in the for sale section..