Welcome aboard! Pretty sure most (if not all) bearings & seals are readily available, as well as brake shoes & hardware kits. Brake drums and gearsets are harder to find but if yours are still good..... Those Eatons are tough as nails and if nothing is wrong with it, why not keep it? Sorry this doesn't answer your question but I'm sure others will jump in with better info.
EDIT: Just in case this old thread has info that might be useful to you:
http://67-72chevytrucks.com/vboard/s...d.php?t=536119