I think you got ripped off. For $800 you could have bought a brand new, direct from Ford 8.8" rear with the gears you wanted. The rebuild kit I got from Summit which included all the bearings and seals was less than $100.
All I can say is that I was glad I was able to do my rear by myself. Sandblasting, painting, and all.

I'm sure you were a lot cleaner.
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351W 89 Mustang GT Convertible