4wd TH400 tranny options/problems dump truck

[cc_bob]

Hello,
My 1986 4wd one ton dump with a TH400 has lost reverse, as a matter of fact in neutral in goes forward and reverse it seems like it is just fighting itself. Put it in park and it goes forward too (parking pawl was broke, I replaced it but the slots it is supposed to catch on are rounded off). Is there any hope to get reverse going again for this tranny (without removing it)? The truck is used very little since it is for my own personal use, plow snow in winter and do a few errands(mulch, topsoil, gravel, etcl) in summer

If it is doomed, I have 2 other used trannies that I am considering due to budget and I can get them for a few favors once the truck is on the road again.

I can get a TH400 from a buddy out of a 2wd, but I do not know if a 2wd and 4wd have different output shafts? If they're the same, can I just unbolt the tailstock and bolt it to my xfer case?

The other tranny I can get is a TH350 that has a transfer case on it. My transfer case has a PTO on it that I need for my dump, so can I swap just the tranny? Or... can I possibly install my PTO in the other transfer case? Is the length the same? Any other changes needed?

Thanks for any advice you can give, I've changed lots of trannies but never had to mix and match before.