I had a F250 7.3 with a smaller Bigfoot and took it to Mexico 4 or 5 times. No problems with the fuel as it has none of the new pollution control equipment. New shocks are probably needed, many of the non main roads by reputation are quite rough and many washboard. Change all the fluids and filters,the transmission may be approaching its service life so it needs looking at closely. Fortunately there are so many of these trucks in the world that it and the old Dodge Cummins are serviceable almost anywhere. I found people in Chichuahua MX who knew more about them then the shop in Colorado who replaced the front ball joints on my F250(F350 not an issue).
When your done, let me know where the truck is and how to get it as we want to spend 6 months there next winter.
