I have a buddy who is in the "Junk" Business and has a few Pontiacs. His personal ride is a '51 Pocahantas Converible, beautiful car . . and he says he has a couple of rearends back there.
I don't think you're gonna find any NOS running gear or driveline parts for something that rare.
But, he may have a couple of serviceable drums that you can turn and use . .
PM me with your contact numbers and I'll hook you up with him if you're interested.