I figured that I've built a few trucks, built my own engines, What the Hell I'll build my own rearend or at least give it a shot. Boy it didn't take long for me to get stumped. Called to order the carrier bearing set, that asked 8 1/2 or 8 3/4 ring gear. Its a 12 bolt out of a 75 1/2 ton truck. I did not realize they had 2 different 12 bolts in the trucks.......... Anyway on the ring gear do you measure the machined surface or all the way to the outer edge of the teeth?