There isn't much you can do with a 3/4 ton rear. I think an OD transmission would be a good approach. However, your bolt pattern is going to be different than the 1948 and later which eliminates most OD transmissions that will bolt right in. Clark made a 5 speed OD that fit the old style clutch housings. It was a popular conversion 50 years ago, but the old Clarks are pretty rare these days. Most of them have been scrapped. Years ago, a friend of mine bought a Borg Warner OD from me that was for a Y-Block Ford and he made it fit, but I don't remember what all he had to do.
