Which heads?

Demonic said
Don't forget to address the drivetrain balance issue. You'll need a correctly weighted torque converter or flywheel.

Good mention. Being he has an automatic, I’d do and have done a B&M flexplate.

BsB Duster said
The car has a 4.30 8 3/4 so gearing shouldn’t be a problem although we are planning to put 3.23 in it ASAP. Lol

I really would not go any lower numerically.
Whatcha got for a tire size?