If you get a 450 or 550 instead of the 350, you will get the 19.5" wheels from the factory, along with larger brakes and some other cool stuff. The only downfall is that with these trucks, the highest gear ratio you can get from the factory is 4.30. I have the 4.30 gears and this thing pulls like a champ! Besides, the 4.30 gears vs the 4.11 gears only add another 100 rpm in overdrive. No big deal. As for fuel mileage, it is pretty much the same as my friend's 350 with 4.11 gears. We travel together a lot and he needs to stop for fuel before I reach 1/2 tank. When I ordered it, I added a second 40 gallon tank to my truck for a total capacity of 80 gallons, but that is another story. Here is my F-450.

Had a 410 in a 99 that was turned up a bit. Pulled a 48' Goose Neck race care trailer with 2 cars and spare everything ( weight= 18000 lbs ) Changed to a 373 and the truck seemed to perform better. That diesel liked to be lugged