FWIW My Challenger has a 650DP on it, stock cam, manifolds, Performer RPM & I've got 64's in front.. But I opened the PVCR .002 so it runs about the same A/F ratio under power but it's leaner & cleaner in cruise mode.. Personally I left the 76's in the rear, when your in the throttle enough to bring in the secondaries you probably want fuel so why lean it out 6 jet sizes?