It sounds like you may be truck hunting.
So one thing to know is that the Ford F350 shortbed fuel tank is about 26 gallons. The longbed gets you a 37.5 gallon tank.
If you get 11 mpg (diesel), then that's 286 miles vs 412 miles range. Based on my comfort level, I would travel no further then 200 miles without fueling up if I had the shortbed version. I just don't like being in a situation where I would be forced to look for fuel that often. I like buying fuel WHERE I want to and WHEN I want to.
I know of at least one time that I got maybe 10 mpg for the entire day (headwind across South Dakota), so it can be worse.
My .02 opinion.
Not saying you have to buy Ford, it's just the one I am familiar with.
