My grandparents owned a 1988 Ford F-250 4x4 460 automatic, supercab longbed. They were retired and used it to travel all over the country pulling a 21' travel trailer. The truck and trailer both were given to my aunt and uncle. Still on the original untouched 460 and transmission. Only things that have been done are routine maintenance, tires, brakes, belts, tensioner pulley alternator, ignition switch. Everything else is still original. Last time I drove it, late 2012 the odometer had just rolled over again so its pretty close to 400,000 miles now I'm sure. Love that truck, and about the only time I use it now is when I want to haul firewood. I'm just glad that its still in the family.
It doesn't get anything for gas mileage but it will pull or haul anything you want with it.