I friend of mine has a 2003 F-250 with the 7.3L Diesel for sale that I am going to look at tomorrow. It has 75,000 miles on it, and I know it has had meticulous care (he is a retired heavy diesel mech...
I tow 13k fifth-wheel with the 01 in my signature, just returned from Yuma to Western WA. I run an old Superchip programmer in tow safe mode and have had this rig in 13 states with several crossings of the Rockies. Replaced torque converter at around 60k miles, a couple of injectors and front wheel bearings only issues in first 102k miles. Expect to be able to get at least 200k miles out of truck.