[gumby79]

Bigest question is are you going to be in snow country during winter?
Then 4x4 is good for DD. For interstate towing chains are required for towing. 2or 4wd don't mater.
Installing the free spin kit, like Skyking did ,will help with rolling resistance 5%@70 but dose nothing for the "tall truck" aero penalties 95% @70 (he saw a cupola mpg improvement) .. if this will be a highway only setup(4x4 is for snow/muck only) then consider lowering. You can maintain your tow capacity with airbags /solid /overload springs . Drop it as low as possible. With my 91 D250 1wd eaves a lot to be desired on ice. Underway it sticks to the ice vary well, geting moving now thats the sore spot, Ive had to put on chains to get out of a flat(albeit 6" of crusty frozen snow) parking spot.