To me, the cost of the truck itself was the least important. Yes, the difference between an M35 and an LMTV may be several grand, but when the operation and maintenance is roughly 10x that of a big pickup truck (e.g. $100+ oil changes, $300 tires, $150 tanks of gas, etc.), not a big deal. Then you start talking upgrades and it seems like every time you turn around you're dropping $400 on seats, or a new canvas, new version of the air drier, specialized tools, or whatever. Cooler upgrades (e.g. A/C, lockers, high speed gears, 290HP engine) are all several thousand dollar drops... pretty much as much as the truck is worth itself. That's what I mean about these being money pits... I previously had big offroad trucks (e.g. K5 Blazers, fullsize pickups, etc.) with big engines and tires, and these military trucks are a whole new level of "big boy toy" with the bill to go with it.
I'm not trying to talk you out of one, it's just that if you're worried about which truck is cheaper and then want to convert to different brakes and run on vegetable oil, it seems like you're misunderstanding something huge here. "If you have to ask how much it costs, you don't want to know" kind of thing. Each of those are probably several thousand dollars of messing around before it works. At which point, the cost of the truck itself is insignificant, you're just paying whatever money it takes to get what you want.