Truck Repair: replacing transfer case, salvage yard, ford f250

Question
I have a 1989 Ford F250 that needs to have the transfer case replaced.  Do I need to find one off another 89 Ford F250, or is there a range of years that would work?

Answer
Hi Jon,
I can't immagine that they stuck one on in 89 that was year model specific. I would assume several would fit, but haven't needed to switch one.
Is the case broken? Or why can't it be repaired.?
A salvage yard could help find what would fit, if you need a different one.
Good luck,
Van