I have (and love) the Ford lineup. I do have a Cummins in a FC80 (it IS a great engine, just dont want what the rest of the stuff it comes with
). I would look for a F-350, you can always get custom rims for it to get rid of the duals if that is what you find reasonable $$. I agree on all notes as to the trans needing to stay cool (drop a 6.0 $550 tranny cooler in and your fine), mileage, manual hubs, windows, etc... we have three boys to cram in the cab so CC/CC long bed for us. I stumbled into my rig and got lucky (under 100K), it is almost exactly what I would have factory ordered. I did upgrade the front seat, and pocketed door panels for travel maps/goodies (XLT), and it had A/C (a must) and found a tilt wheel column to throw in. Basically other than cruise (perhaps someday) it is a great machine for what I do. I did put F-450 spings and mounts on the rear, and went to 19.5" tires for durability. Mine is "anti bling" and needs a silver/grey paint job and some F-550 flares. Good trucks, I have a 00' 550 4x4 work/crane truck, and sold another 00' that was a 7.3 manual 2x4. Also, if you plan to run highway speeds with the hubs locked in rebuild the front driveshaft, more than one person has taken out the tranny AND transfer case housings when they "GO". I rebuilt both of mine as insurance as it is a $4500+ parts bill IF you can even find them.
A note on the manual vs auto tranny, while my old manual 7.3 550 could pull a house, the auto keeps the turbo "spooling" (under power/pressurized) and delivers a much faster and effective pulling truck. I like the auto, especially around town. You just GOTTA put hte 6.0 cooler in it. Also, a tranny and coolant filter are GOOD ideas for long term durability. See FordTruckEnthusiast for lots of tech details, by engine and truck size....
http://www.ford-trucks.com/
Buy the one ton (or 450/550), and you can trailer your Liberty and not even effect your mileage. Look in "Truckpaper" good source.
http://www.truckpaper.com/
Also, a dealer n Kentucy gets ALOTof fleet units, it is Larry Stieger (spelling) that might be a source.
http://www.stigerstrucks.com/ looks like there are two nice ones a 7.3 F-250 and a 350 on there now. Both are well equipped (Lariat, and XLT)
DO NOT take the statement about the 6.0 LIGHTLY, you do NOT want one..........
Jronwood