Try locking out your dizzy at 35 and hook the vacuum advance to manifold vacuum. You'll have to dial back your idle, but it should help considerably. You can always swap it back to what you have if you don't like it. Your low end responsiveness and mileage should improve significantly.

1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)