Saginaw trans help, any trans guys out there??

I've got a 3 speed saginaw trans that has been sitting outside, and looks pretty crappy on the inside, but i was thinking about tearing it down and seeing what is still useable, and i also have a 4 sp saginaw thats in really good shape, all internals are really nice. I want to rebuild a 3 speed for a spare because thats what i run in my car. My question is, are there many of the parts between a 3 sp and 4 sp that are interchangable? I was thinking about tearing them both down, and whatevers interchangeable useing the good parts from the 4 sp to put in the 3 sp. Also, if anyone has any tips, tricks or advice on rebuilding a saginaw it would be much appreciated. Thanks

Maybe this will help.

http://www.circletrack.com/drivetrai...ssion_rebuild/

take 1st an 2nd outta the 4 speed an put it in car,..take 3 speed outta car an put it on trailer as spare,...take junk 3 speed an put on shelve after cleaning for spare parts...what i would do...