I am not an expert on Ford diesels, but I would not touch one of the "lawsuit" Navistars. Ford folk on this forum can help you identify the problem years.
Beyond that, I would get the biggest, baddest shocks you can find for the truck because of the weight you are carrying and the state of some roads. I am using Fox external reservoirs on my truck.
And, off course, flush the radiator, transmission, transfer case, engine, brakes, etc., somewhere where you can get the correct fluids and filters.
Beyond that, have a great trip and dress warm for the Altiplano.
