Originally Posted by SkyBound
If you haven't already bought the truck I would advise you to step back and think about it before you do anything. In my opinion there is no point in buying that truck with that engine if you plan on towing anything. There's really no benefit - your fuel savings will be minimal if any and all you're going to get is a nice truck that struggles.
You already stated that you're thinking about upgrading trailers to something larger, so why would you voluntarily handicap yourself with respect to your trailer choices? The F-150 is an awesome towing vehicle if you equip it properly and the base model V6 is not what you're looking for in a tow vehicle. Look at the 5.0L or the 3.5Eco for towing. This will allow you more flexibility for future trailer upgrades and an overall more pleasant towing experience. You're really not saving much with the base V6 option.
As long as your stepping back consider what you think you might be upgrading to regarding trailer in the future. The F150s are very respectable, but even Dodge's and Chevy's are looking great. Perhaps consider going in ugly early, and look at things in the 250/2500 range. Even they are getting decent gas mileage these days as daily drivers.
Throw a load in in anything and hook a trailer on it, and fuel mileage will go down. The question then becomes, how safe and capable do you want to be while towing?