Need Help with T50 Eaton Rear End ID

[sweepleader]

Yup, I am convinced you are right on with the exception that I doubt the diff has been changed. It still has the same red paint as the rest of the chassis, applied by the maker of the fire body. The truck only had 4600 miles on it when I bought it, less than 6000 now. The build sticker says H170 and googling that with Chevrolet brings pretty much the same thing you found. I also found that it was made in a two speed version that has even deeper gears! So this looks like a dead end, at least as far as my hopes to reduce the ratio. I do appreciate your efforts, thanks again.