x2 on diesel engine issue, it needs to be 2006 or earlier to avoid ULSD fuel problems in LatAm. A basic (non-turbo) gas engine like the older Ford and GM vans, or perhaps the newer Transit 3.7 or Promaster gas engines should work too.
But I don't know of any factory produced Class B that's well suited to LatAm expeditions. RV dump facilities aren't available so cassette, composting or porta-potti toilets that can be emptied in a normal bathrooms are needed. Vehicle mount propane systems can't be readily refilled and are pretty much useless once empty. But that's OK because the Topes (large speed bumps) and potholes would pretty quickly tear them off along with any low hanging generators, tanks, valves and running boards.
Due to these reasons most LatAm travelers venturing beyond the Baja RV resorts purchase a separate vehicle for the trip. Pickup campers are popular because they often have simple porta-potti or cassette toilets, use standard 5 gal propane cylinders that can be exchanged in each country (valves vary by country but a few adapters will suffice), and have internal water tanks that don't protrude below the vehicle.
Van based units are certainly possible and have the advantage of a fully enclosed space between the RV and driving compartments. Older (2006 and earlier) Sprinters, VW vans (for the mechanically inclined) and Ford E-series vans are popular.
Custom van converters like Sportsmobile, Van Specialties or Outside Van could fabricate a new Class B suitable for LatAm travel. Start with a gas engine chassis, perhaps an engine generator, cassette or composting toilet, internal or skid protected water tanks, Webasto petrol fired heater, cooktop that can use 16oz (Coleman type) propane canisters that are widely available in Latam.
Expedition Portal and Sportsmobile forums have lots of information from travelers either planning or having recently completed LatAm adventures. They're also a good source for buying gear for a trip or reselling units when travels are complete.