i suggest checking the gear ratio.

jack up one wheel and put the car in neutral. turn the wheel one full turn and count the turns on the driveshaft. multiply by two.

i suspect you may have a 346 rear end.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.