Ecodiesel 10,600lbs, F150 13,300lbs... when are you ever pulling close to 10,000lbs? I would guess, never. It's got a lot more with it being a half tonne chassis then it does the engine.
Also, if you are pulling a trailer with that much weight, you're buying a Duramax, Cummins, Powerstroke.. Not a 1500 series truck.