Build me a 451 stroker

Or a 4.25" crank for a nice 507ci stump-puller. Having driven one (in a 2-ton B-body wagon), all I can say is WHOA. Pulls from 1000RPM in fourth gear. (Yes, that will take some careful part selection to work on the street.)

You won't need 3.91 gears with that (even a 470) in an A-body...heck, you could run 3.23's or even 2.76's and it would still scream!