Well the slower dart I have with the 8 3/4 runs in the 6:50 range now foot break cal tracs and a small shot on the 383. No issues with the 8 3/4 and it leaves with the wheels in the air about a foot... a 6:90 is equal to a 10:90.... My car is all metal except for the bumper hood and some lexan. Just something to think about...