Matt I do my measurements off the pad where the pinion snubber mounted if the rear has one if not some flat on the same angle as the yoke and the same on the tranny. the question is whether you set it of the tranny or the drive shaft.I have done both and both worked, I just choose to parallel them these days. it just makes more sense imo. find zero point if you choose the parallel choice. if the tranny is 3 down the rear needs to be 3 up to find 0 then roll down how ever many degrees you want it set. hope that helps.