'64 C-10 Transfer Case Info Needed

[C10 - C90 Bill]

A friend of mine has a '64 C-10 4X4 with the rare Factory Original 3-Speed Trans. His Transfer Case is making noise and is popping out of gear. Need to find out some info on it. Does a C-10 with a 3-Speed have the same Transfer Case as a 4-Speed Truck? Also wondering how available are parts for the Transfer Case he has and is there such a thing as a Rebuild Kit available? And what does it sound like is wrong with it?

Any helpful info would be appreciated.