V6 or small V8, overdrive transmission and 3.55 rear end or so and you're set, unless you have a heavy load. Just don't drive fast; the poor aerodynamic profile of a pickup is something that can only be improved so much.
And things are only going to get better - the Chevy Volt is in the works, (still subject to some criticism, but I kinda like the idea of a plug-in hybrid) and Ford is RUMORED - RUMORED RUMORED - to be working on an F150 that uses a hydraulic hybrid system that doesn't involve batteries. (Regenerative braking compresses a nitrogen cylinder, which in turn is used to help you start again - good for stop n' go traffic.)
Again, this is only a RUMOR that I'm trying to find out more about myself. You might be interested in if you can wait...
Just my .02...
Cool rumor.
Thanks. Maybe they could even put one on a Ranger. :)