Scored some cool parts today from a local salvage yard. I got a ZR2 rear end with 50K on it. It's an 8.5" ring gear (mines 7.5) and has the factory limited slip/locker, and has a 4" wider track than my stock diff matches the front better. Popped the cover looked to have never been off, and looks perfectly clean and hardly any wear.
Also got a ZR2 cast iron front diff (mines alum) with...wait for it....... 0 miles!
This salvage yard has a contract with Gm and get a lot of test vehicles and all kind of stuff that has to be ddestroyed or parted out. They'v parted out pperfect zo6's and all kinds of Gm vehicles. Anyways this was exactly what I was looking for and never would have believed I would end up with a new one.. pretty amazing as it has to be like 12 year old! I'll take some better pics later. Both diffs are 3.73 (mines 3.42)