Great looking truck, I have a fargo in the same color scheme

A Chevy Dana 60 will fit, the difference in spring pad widths isn't much. If you are swapping in a newer drive train/transfer case you will probably need a drivers side drop transfer case So Ford, or adapt a newer one.

Edit: I forgot its also 2" narrower, still better then accidentally buying a Dana 61

If it was me, I would wait until cummins announces a new repower the current 2.8 is probably a bit small. The easiest would probably be a 5.9 magnum, I like the idea of a gen 3 but I am not sure about getting a flywheel for the truck transmission to work.