No matter what method you use to establish the pinion depth in the rear, the best way to verify it is to examine the resulting gear mesh pattern with marking compound. We messed this up the first time by slathering too much marking compound onto the gears, which made it impossible to discern a clear pattern. So apply the compound sparingly to two or three sets of teeth and rotate the gears a few dozen times until a light pattern is transferred onto the gear teeth. Then consult a gear pattern chart to assess it. The pinion gear teeth should mesh with the ring gear in approximately the center of the teeth, both horizontally and vertically, to ensure sufficient engagement and quiet operation on deceleration. We incredibly got the pattern dead nuts on the first shot.