1985 F-350. 6.9 IDI, 4 speed + 2 spd Range Splitter. Gets 14-15 mpg empty and 12 mpg with my '24 enclosed (10,000 lb capacity) hanging off the bumper.
We used my buddy's '14 F-150 (5.0) and my trailer to go get a '59 Merc M-100 Panel Truck out of Winnipeg two summers ago (I hadn't purchased the '85 yet, and my '76 F-250 had the tranny out of it.) The F-150 had plenty of power , but that enclosed would walk the F-150 all over the place with a cross wind (I-29 across eastern No-Dak), even with the load leveler. The trailer doesn't do that to the F-350. I can load my '62 Merc Monterey wagon (Think 5000+ lbs of car) into the trailer, and pull it comfortably any where I want. The 6.9 is a bit down on power compared to modern diesels, but the range splitter helps that alot, and it will soon get a Banks turbo kit as well. Being all mechanical, no DEF, no emissions equipment, and stupid reliable makes up for some of it's other shortcomings.