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Good Points. Well for what I need it to do.... Maybe I should be looking at a 2 1/2 ton Deuce multi fuel...? I was hoping to find something like a deuce, only smaller.If you're going to be off road that alleviates a couple of things you would almost positively NEED to change. Stock engines...well, Bob covered those well but if you're really going to use it, a little more grunt would be nice. Off road, you will not need to swap out the NP200 T-case. If you plan on maintaining decent highway speeds it seems that only a licky few have had the NP200's not overheat with engine and overdrive trans swap crusing at highway speeds. It's a WWII T-case designed for 45 max in a day where 35 was common now being asked to hang at 55-65mph. It also has both front and rear outputs off the lower drop which builds more heat as driving the rear ALWAYS has to go through a gearset and not a straight through design like the later NP205. The 205 are close to being bolt in but you will need to fabricate the driver's side mount.
Easiest thing to do for the driver's side is to make a 1/4" plate cover for the PTO then make your mount to fit the stock crossmembers. Pass side easy was is to take a 205 mount and the stock 200 mount, overlap them and weld together. Simple and done.
I've had SBC and BBC in a M715 and they're both great combinations.
Stock axles will get most people really stuck. Stock axles with lockers and Mile Marker Selectro's, and good meaty tires will get you where you want and back out again. I ran mine with lockers, Selectro's and 37x13 TLS BOGGERS on stock wheels with a 427BBC and 3053A overdrive for a couple years with no problems whatsoever. Eventually it got a Rockwell axle upgrade and 1100x20 Goodyear Custom Extra Grips (measured 42") and was a GREAT road truck. Best example I can give of its road manners is this: M105 deuce two wheel trailer (not a light trailer) with a surface grinding machine (about 1,200 lbs) and a Bridgeport J-head milling machine (about 1,800 lbs). I had about a 75 mile return trip with that load up the hills of Penn's Woods and didn't have to drop out of fifth gear. The truck looked really well with the spring over conversion and set of Rock's under it and the 42" Goodyears fit the fenders nicely. I actually got pulled over 3 times for credential checks with the Boggers and not a single time with the truck higher and bigger with the Rocks.
From there it went to 46" XML's and street driving was concluded especially for PA's vehicle laws. We did have fun at Top Truck Challenge though-
Anyway...any engine you can pretty much think of has been in these from 4 and 6 cyl Cummins to Caddy 472 and 500's to ANY SBC-BBC, 6.2's and 6.5's or Ford SB or BB or even the mopar guys have wedged all their engines in too. It is a platform for creation. I think one of the best swaps, though a cost a little upfront is the CUCV Dana 60 and 14 bolt swap. Later model axles with stronger parts, disc brakes, standard 8 bolt lug, and 4.56's instead of 5.57's. That swap is HUGELY helpful in making the truck comfortable on the road.
The transfer case is divorced mounted so almost whatever engine and trans you feel like can be put in. Quite a few have gone with the 4BT Cummins and several of those with NV4500's. It's a good swap. Down and dirty if you have the time is the CUCV axle swap then SBC and TH350 or 400 and a 40" tire. Bang, done, drive. They ARE a tough truck.
at the least. 
