Why not a divorced NP205? They're not that hard to find, and they don't come much stronger than that.
Also, bread trucks sometimes had 4cyl cummins in them with a chevy turbo 400 trans behind it. If you could find one of those, you could always gut the th400, put a 4x4 tail end on it and go with a chevy style t-case.
Just throwing ideas out there, I don't know the specifics of your project.