What kind of rear end is it that came in the 67-72 3/4 ton chevy's. The ones I have seen have third mwmbers and I beleive they are made by Rockwell. They look to be very stout rear ends the reason I am asking is I have access to one and I was thinking of putting it in my 72 Jimmy. I was also wondering if parts are readily available for these rears? Do they make an air locker for them? Any help would be greatly appreciated. Thanks Eric M.