Rear end leaf spring perches

[67chevy4x4]

I'm replacing the rearend in this rebuild project with a rearend from a 76 chevy blazer. I need to know where I can find the correct dimensions for the leaf spring perchs and the pinion angle. The rearend that I took out of the truck was not original and was modified so I can't trust the work done before me. I can always measure the dimensions for the perches on a different truck but would like to know if there is a source for this information. Does anyone know where I can get this?