Bearings, bushings and seals are what get replaced in a rebuild. I was able to get all of these for my 62 k20 from rockauto, truck and car shop, etc. Rebuild was not too difficult. Used the shop manual, and there is lots on the Internet about it. Something to consider if you have no other choice and the internals of your box are not too bad. I was happy with the results. Spares and cores ate scarce. A lot of the rebuilt units on the Internet are actually rebuild services of your existing box.
