Still, how about the exhaust? Is it limited to a single , or are duals allowed? And '66 D-Darts had headers, but itäs a "package car", so I have no idea wether itäs allowed or not. The early Darts have 111" wheelbase, just like the newer ones, and they have a pretty long rear over hang which might be good for the weight distributiön. However, the GT is not that light. Even though they are narrower than the new ones, they aren't any lighter and the Hard Top is the heaviest of the bunch. Most competitive would propably be a '64-'66 valiant 2 D sedan, with onyl 106" wheelbase and the same drivetrain available they have considerable more potential than the 300+ lbs heavier GT Dart. A 7 1/4" with a sure grip should work at least for a while, I had one behind a 340 and a manual and couldn't kill it. the open ones are a different story, the spider gears die within a few days, and when you weld it solid, the axles will break.