Panamericanos, You are on the right track. Subscribe to some of the major truck camper forums, like the truck camper forum on RV.net (which has a big and heavy bias) and https://www.expeditionportal.com/forum/ (which has an Anglo/European bias)
to see what others in your shoes have and are currently doing. A few observations:
1. Unless you are getting way off the main roads in North and South America, you don’t need 4WD. Just having a locking rear diff, or limited slip should be enough. A Detroit/Eaton Tru Trac is my current fave. No clutches; all gear driven; torque biasing; transparent. I’ve had 13, 4WD’s over the 50 years I’ve been boondocking and Jeeping, and actually go looking for out of the way places to wheel, but on this long a trip, you don’t need it. You probably won’t be doing this:
which was last week in the Anza Borrego Desert in CA.
2. A diesel engine is a plus, but be aware that most diesel pickups in the U.S. built after 2007 for ultra low sulfur fuel have Urea canisters and D.E.F.tanks that are not friendly to Mexican and other only low sulfur diesel fuels in Mexico and So. America. Search D.E.F. and Mexican fuel. A gas engine is not so much fun either because of the high fuel consumption compared to diesel.
3. If you are going to live at length in a truck camper, the rule of thumb is to have more living space and amenities the longer you are out.
4. Research the wheels off your project and take an RV guru with you when you purchase your camper. They can detect flaws and maybe negotiate a better price for you. Same with the truck to carry it. Be prepared to cast your net far and wide for each, up to 1500 miles from your location.
5. Once you get all your ducks in order, camp out in your driveway for a few nights without going into the house for anything to see what you need to make it work once you cut the umbilical. Are you going to need a generator?
6. I’m thinking air conditioning in So. American is going to be prohibitively expensive to operate, so you might consider a 4-season, hardside camper that will give you more hours per day of livable air temperature. At a minimum you’ll want one of those ‘fantastic fans’ in the ceiling. Ours works amazingly well.
7. Another thing is Propane is not as readily available in Mexico or So. Am. as it is in the U.S. so that’s another thing to think about.
8. To really stretch you power allotment, 200-300 watts of solar, all LED lighting, and a minimum of electrical appliances will be a lifesaver.
Oh, there is a lot to consider, and Mike has covered many of the essentials, but you will develop your own stamp; your own style of operation and needs vs. wants over time and this takes time to develop. One school of thought is to just jump in with both feet,make your own mistakes and enjoy the adventure wherever and whatever comes your way.
2020 Ford F-350 XLT FX4 4WD SRW SB SC 7.3L Godzilla Gas TorqShift 10R140 397 amps dual Alt dual batts Frnt Dana 60; Rr Dana M275 E-locker 4.30's 4580/4320/4066# payload 7243# curb wt. 11,300# GVWR 5-er prepped. 2020 Northstar Laredo SC, 12v compressor fridge, cassette, 320w Solar sub zero insulation.