i have a 91 5.0 and i want to put a c4 behind it. i found a good tranny but im sure if its right for the car. do i need a10 1/2 bolt circle or 11 7/16 what about case or pan fill then theres the converter spline what is best and will it bolt right in or do i need driveshaft and crossmember mods? the car was a five speed. the tranny i found is from a 68 mustang. what is it?? also what flex plate do i but 28 or 50oz and 157 or 164 tooth??????????????