I've used the instructions from the MP Chassis Manual to check/set pinion angle... its hard to explain the steps in a post. If fine adjustment is required wedge shaped shims under axle mounting pads are normally used to adjust the angle. The chassis manual and shims are available from Mancini Racing.

I've got the same question John had... did you change rear end sizes (say from 7 1/4" to 8.75)? A pic would help showing rear and driveshaft in rough mounting position.