I had an F-350 diesel. You're right, they suck on the trail. In fact, a trip to Moab with it was what prompted the entire RV redo from that truck and a 31' trailer to the current 40' motorcoach and Commander. The XK has been 10 times the trail rig.

There were times in coral colored Moab sand, that the F-350 spring-hopped across where I really didn't think we'd make it past. Get it stuck, and you have an 8,000 lb. truck to extract. Switch backs were 47 point turns. Of course, it was an extended cab with an 8' box. 5 MPH was max. Any faster and we'd rupture spleens.