[chris vickery]

Hi John

There are all sorts of things that you can do with that project. If you have looked already, you may notice that overseas (UK and Australia), that motor swaps are commonplace. I think in Europe the Perkins is especially plentiful and inexpensive plus the fuel prices on diesel being more economical.
If you want to maintain a military "look", brouse around websites for used military vehicle parts. You may be able to find an appropriate deck that will fit perhaps cheaper than what you can build one for. I like the larger tires and 4BT Cummins idea.
I think that your stock axles are plenty strong to handle anything, the only downside is the ratio. You could swap some deuce axles maybe or 5/4 Chev axles from a CUCV M1008 or M1009 which would get your ratio down.
Looks like a fun build.