it depends on what you have done to the heads (have you milled them any?) and maybe one or 2 other factors that I cannot think of right now. I am sure you can get some more replies on this one...
actualy this not for my truck, i fignaly got the mustang a driveshaft. the car is an ex-4 banger that i shoehorned a 521 into. I got a deal too good to pass up. the truck i am going to leave alone.Anyways the car weighs around 3400 i think 9" with 3.73 spool, c4 full manual.