Looking for more 408 pull at the big end?

Either the tune up is WAY off or the heads don't work well.

Brians Duster went 96 with 408 making about 480hp at 3350# with a 4.56 gear and hughes 3500 shelf converter.

Timing, jetting, air to carb, something isn't right as the MPH is way down. If your car is lighter than Brians, It's REALLY off tune wise.