Well since I'm kind of new at this, I did some research on how to measure the angles, and that's what I did..then I read about what other people have done for this kit, and I decided that a 6* would be a good place to start. I measured the angles again once I put the shim in to make sure I got it where I need to be, and right now I'm within 1/2*. I got the shim kit from Summit racing, just search for a 6 degree pinion shim.