difference between hydro and mechanical rocker shaft diameters

CHEVY BOY-----------

I have no idea what that means.

Larry's books on differentials was a bit of a disappointment. No where does it mention the master pinion depths for the 8 3/4 carriers. Figures though, the FSM doesn't mention it either. Plenty of diffs get assembled without it, but if you have a depth mike and a bit of skill.....