Any 5.x L gas burner will pull a rig your size, but obviously with reduced fuel economy. You have to ask your self just how often will you be towing and how long are the tows. I pull a 25' camper with a F150 5.4L 373rear end, but it is on relatively flat ground (LA, east TX, AR, MS AL). I pull a 30hp tractor and gear as well. You have to realize the pulling power of a gas burner is adequate for occassional pulling and moderately distanced towing as well, you just can't drag race with it or cruise along at 75 or 80 mph. As for the diesels go Ford keeps changing their motors for two reasons. 1: They haven't developed a motor that will give the needed fuel economy along with the required power that will burn low sulfur diesel and more importantly 2: They are a majority owner of Cummings Diesel and Cummings has a lucrative deal with Dodge right now. Until that contract expires, Ford won't make waves with Dodge which would jeopardize the Cummings contract. I've been told the new 2011 6.4L F250/350's will only produce 15-17 mpg hwy not towing. My pops has a 2002 F350 7.3 liter getting 19-22 mpg hwy not towing 15-17 towing. It's just not justifyable for my needs to spend the extra $ on a diesel (purchase price and routine maintenance) to to what I do that a V-8 gas burner can't do. Sorry for the rambling, that's just my $.02 plus $.02 more.
