Tigger,
Congrats on the new truck. I have a 2011 F350 Lariat, dually, crewcab, long bed. First year of the new 6.7 diesel. Love it. Had an 08 F250 CCSB with the old 6.2 diesel. It had good power, but the fuel mileage was horrible. This 6.7 makes as much power as my old 02 with the 7.3 diesel and $3000 worth of mods. It's also wider, taller, longer and 1000 lbs heavier and gets the same mileage as my old beloved 02.
My short bed 08 only had a 27 gallon tank. That sucked when you were only getting 12 mpg around town and 8.5 towing. I literally stopped every 200 miles towing. My 2011 has a 37.5 gallon tank with the long bed and I have a 60 gallon, gravity feed auxiliary tank in the bed. 97 gallons of fuel at 9-10 mpg towing makes for a nice cross country tow. I can almost make it to the Fort without stopping.
j