ive got a 4.30 gear and a 31 x 16.50 mickey et street 606 hemi pump gas, 9.60s at 142 mph. shift at 6800and traps at 7000, 2700rpm at 65 mph on the hiway!! ati blown fuel convertor [ cause i broke all the other brands ] we have a 64 plymouth with a indy 540 cuin 3400 lbs with a32x14tire went from a 488 gear to a 456 it picked up 2 tenths and 2mph we are going to try a 4.30 next should pick it up another 2 tenths and more mph for sure best time is a 9.46 at 141 !