The diff was a GM "corporate" differential, which means it's not a chevy/olds/pontiac/buick diff. Maybe made by Eaton, not sure about that. The discs are available, though, both from GM and from aftermarket. I have no idea whether the same discs will fit the corporate that fit an Eaton. I know that the GM differential uses "S" shaped springs to preload the clutch packs, while the Eatons use little coil springs, about the size of valve springs. When you rebuild one, it is possible to put an extra disc or two on each side, and that makes them lock up sooner, and last longer. Or so I am told.