Cracked NP-208

[leegrady]

I have a '81 GMC k2500 (long bed) with a four speed manual trans. The NP-208 is cracked and it seems it's easier to find these transfer cases mated with automatics rather than my four speed top loader.
How hard would it be to change the parts over so the automatic mated t-case will bolt up with the manual trans? I'm thinking the t-case input shaft will need to be swapped. I'm good with trannies, but any skinny on the subject will be greatly appreciated before I take a sack lunch to the bone yard.