What camper set up are you planning on going with? I am not an expert on Toyota vehicles, but just like a USA full size pick up like a dodge ram, I am not sure how much more parts available there would be for a USA built Toyota. I imagine maybe things like door handles and windshields etc. you might be able to find but major engine parts might pose an issues.
My experience has been great with the 2nd gen 12 valve Dodge Cummins. I had a 95 with an automatic that made multiple trips all around Mexico and also all the way down to Nicaragua and back. I had one small electrical issue with the switch for my headlights but funny enough it was fixed with a Toyota part. They are pretty resourceful down there as you know. I had no other problems with that truck and when I drove it down there it had high miles around 220k on the odometer. I did not have a camper on the back but I did have a shell that was filled with about 200 gallons of vegetable oil. I later sold that truck and "upgraded" to a 97 Dodge Cummins with a 5 speed manual and the hardsided camper in my signature. I drove my current truck all through Mexico a few years ago with the camper and also down to El Salvador. The only issue I had was with the manual transmission but I made it work and fixed the issue when I got back to the USA. It also has an exhaust brake which is amazing, it really comes in handy with or without the camper. Not sure if you guys on your trip ever made the drive down to San Pedro on Lago de Atitilan but it's a notorious decent, people burn their brakes up all the time going down, with the exhaust brake I tapped the brakes maybe twice. On the way out it was a breeze, with 350 hp and the torque of the cummins even with the camper it doesn't even sweat. It's so steep that Westies and other underpowered vehicles have been known to need a tow just to get up the hill.
I know of two 2nd gen Dodge cummins that have have done the entire Pan AM, one was a regular cab with an alaskan camper the other was an extended cab. If I was to do something like that beyond just my trips to central America, my choice would be the Dodge Cummins with a regular cab and a flat bed with FWC Grandby. That would be the ultimate set up in my mind, either auto or manual, there are pros and cons to each transmission. A built automatic is pretty nice actually.
I get really great fuel mileage, I know some people exaggerate, but driving like a grandpa on the freeway with stock tires and no load I can get 21-22 mpg. With the camper and my oversized tires WITH the camper I am anywhere between 14 and 16, with my large hardsided camper I consider that very well. I know of a Toyota Tacoma all kitted out with a flatbed FWC was only getting 12 MPG! And the power and torque of that does not compare to the fullsize Cummins. I also really like the interior space of the fullsize pick up. sitting and driving is really comfortable, I always felt kind of cramped in a Toyota compared to my truck.
I would consider a flatbed grandby for my current truck but because I live in my camper for work sometimes over 6 months of the year I need the hardsides and full shower.
Good luck with your search, I have really enjoyed your videos, and will be making my annual trip down to Baja again this year after Overland Expo.