Mopar Cam 284/484 or 288/497

You can install it 6-8 degrees ahead, but you must verify P/V clearance whatever you do.

A 3.9X gear is pretty low (high numerically) by today's standards. That cam installs at 106 by Chrysler, so to be 6 advanced you'll be at 100. I can't imagine you needing the intake hitting max lift much quicker than that.