Throttle linkage geometry

You only have two choices, move the carb end closer to pivot, or bend the pedal up higher. It's real simple geometry. Well I suppose you could move the cable to pedal attaching point, further from the pivot....... but then it won't go thru the firewall in the factory location.....

I too have a 750DP on an AirGap, on a 360, with a 70 Duster pedal in a 68 Barracuda. But with a factory cable.
I am using the Holley/Mopar adapter, and I did have to bend my gas pedal up a tad higher.