turbo 350 tranny question

[tazmaan]

Hi all,
I am new to automatic transmissions and have recently purchased an old 80 Chevy 3/4 ton 4x4 truck. The transmission is already failing, reverse does not work any longer. I am trying to find a used rebuilt tranny and have a few prospects, however I believe there is a difference between the turbo 350 for 4wd or 2wd? Also, the one I am interested in states in the ad it's a 'long shaft'. I have no idea if I have a long or short shaft and how to go about making sure whatever turbo 350 I get will work with my truck.

Any help is greatly appreciated!

Thanks
Jim