I have a 75, and of all the things on my car I would do, replacing the rear bearings is NOT one of them. There are some highly mechanically inclined car owners on this forum, and they can describe it in detail, so if you're looking for the 'ultimate' challenge repairing your car, I'd say go for it. Otherwise, either get rebuilt assemblies from anywhere (Corvette America, Eckler's, VBP, etc.), or take your car somewhere that knows how to replace C3 corvette rear bearings and pay the bucks to have it done. In my mind, it's not worth the heartache, pain, blood, time and money to try it myself only to have to have it redone by someone else. My brother-in-law is a mechanic, and I'd trust him to help me change the clutch (which we've done), and do most engine work, but the rear bearings are 'special' on C3 corvettes, and I wouldn't trust him to help me with that. All that just to accentuate it's not an 'easy' job, and if you want it done 'right' sometimes knowing when not to do it yourself is just as important as the motivation to tackle it on your own.
Frank