When you're out shopping, ask the dealers if they've heard about Aerolids. Home - Aerolid
I've got one of the prototypes on my F-150 and haven't had a tank below 20mpg in months. Details: gear hauler - 2006 Ford F-150 STX Fuel Economy - EcoModder.com
I think that's better than some of the EcoBoost trucks are getting in real life. The guy that designed them and built mine keeps trying to sell them on fuel efficiency alone, but I think they just look cool, and the lid lifts off easily to use the open bed. Maybe if one of the manufacturers hears from a dealer, these will be available for when I'm ready to buy my next truck.