With the Cummins 4bt you don't have to beef up the suspension. The 8.8 rear diff or "bigger" is fine. The AOD isn't a good fit. The E4OD can be used, but with auto trans it takes a lot of work to get it shifting at the right points. The M5R2 is OK for "regular" use and light 4x4 (snow, mild mud getting to the fishing hole, etc). Anything else and you'll want a ZF5 or better. As long as you keep her around 350 ft-lb or less, the M5R2 should be alright. Again, speaking totally from the research standpoint right now as I haven't started my swap...yet.Chances are with any diesel you will have to beef up the suspension and drivetrain.