Dana 60 S60 or Ford 9"
My Dart has a S-60 under it and I'm not making near the power the OP is planning on, but if I were doing it over I'd buy a 9".
Go to any of the races where really fast cars (3.70's- 4.20's) are running and take a peek under them and see what's there. Heck, look under the Drag Pack cars. If there was really much difference in the HP required to run the rears you'd see a bunch of Dana's in the heads up classes.
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