You are taking the trip I always wanted to take. Alas, time waits for no man, and @ 70 anos, it's too late. A lot of what you will attempt has to do with your chronological ages. When you are young, the crustier, the better. As you age, you go through stages of decomposition that direct you into the lane with more comfort for long distance foreign travel. If you have a good attitude, go for it.
We are not done yet, however, doing a 16 week, around the U.S. boundary states, clockwise, camping ON every beach that will permit it, trip in our TC and that will have to suffice. September 1st to New Years Day.
I do have some advice from someone who has driven over a million miles in vehicles with a low range.
1. Keep it simple. You don't need or really want all those add ons. Too much weight. The farther you get away from stock, the higher your likelihood of part failure. You may not even ever get into 4WD let alone low range. Sniff around Expo and read of those who have done very long, even years at a time, trips to Timbuctoo and back.
2. Take a small, lightweight off-road trailer along (maybe even with a RTT installed to keep you off the ground when the monsoons hit, assuming you are doing some camping). Go to the Expo trailer forum on here, simply the most inventive people around these parts. The longer you are out, the more you will appreciate some actual space for your stuff; like self recovery equipment. Back in the day, first two, then three, then four of us would travel and camp out in a Toyota FJ40 and later an FJ55. Things got a lot less stuffy when I started pulling a ConFer Toyota Jeep trailer behind with locking lids (and we added a tent boot to go over the tailgate hole). The Con Fer was pilfer-proof, bullet-proof, waterproof and would float when fording rivers. Eventually, after 12 four wheel drives, we settled on a truck camper for long expeditions to anywhere. What were those conveyances, you ask?
'49 Willys Ute Wagon; '66 Toy L.C. FJ40; '70 FJ55; '80 Scout turbo diesel Traveller; '82 Jeep Scrambler (CJ8); '73 Jeep J4000; '89 Jeep XJ; '90 Jeep XJ (I rolled it off a cliff in Telluride); '99 Jeep XJ; '01 Dodge 2500 CTD; '04 Nissan Murano SE/AWD; '11 Jeep Grand Cherokee; '08 Kioti 4WD, 3 cyl. 35HP diesel tractor. I had a '42, M100, WWII jeep trailer, a '67 VietNam era M-714 Jeep trailer, the '67 Con Fer Toyota jeep trailer, a '55 Bradley jeep trailer, a '65 homemade jeep trailer, a converted horse trailer to trash trailer we call 'White Trash' (because of the bears and no trash pickup) and a 14' car trailer.
A CBS (I think) producer went around the world in a small, sporty, AWD, MBenz towing a matching and locking fiberglass jeep-type trailer and it worked well for them. There is a write up somewhere on the net, and I think he wrote the obligatory book about his adventures. It was fascinating hearing of their experiences.
If I were to pick an appropriate rig for Sud Amerika, it would have to be a Toyota something, or a MB something, or a Japanese small truck of some kind. Why? Availability of parts and service, and it's what they drive there.
Failing that, I would pick the legendary Jeep WK Cherokee (1999-2004) with the simplest set up. You would have space and comfort, solid axles, fine drive system, plus reliability. Then again, you probably can make anything work if you are set on it.
Unless you are very recent backpackers that enjoy the challenge of no space and carrying everything on your back, you will enjoy some space.
It is assumed you will do a blog of your adventures, no?
regards, as always, jefe