The other gotcha is unless you go back to a really old small truck you don't get any fuel economy gains. Once they started adding auto transmissions and A/C and everything else the fuel economy averages around the 20mpg mark for small and full size trucks. The older 4 clyinder manual transmission, no confort items trucks could get decent mileage but those are getting harder to find.
You stole my thunder! :elkgrin:
Yeah, don't assume just because it's a "compact" truck that it will get decent MPG. A Ford Ranger or Mazda B4000 (like the one in your photo) with a 4.0l V6, auto, 4x4 and AC would be lucky to get 15 - 17mpg without the camper. Add the extra weight of the camper (which is very close to the max weight capacity of the truck) and you would probably struggle to break 10mpg.
The truth is, most modern "compact" trucks, especially 4x4s, really don't get that much better MPG than a full size truck. And you can get a diesel on a full size, which will improve your fuel economy somewhat.
Another consideration you've got to think about is what having all that weight way up high will do to your handling. Forget about going on any moderate sidehill, that's just a disaster waiting to happen. I imagine there are people who take cabover campers on 4wd trails but there's not enough gold in Fort Knox to get me to do it. Even on the highway, imagine what would happen if you got hit by a vicious crosswind. With the smaller size and narrower track of a compact pickup you'd be at the mercy of the wind.
Another option, as others have said, might be a small travel trailer. Of course, a trailer will limit where you can go, too.
Honestly I'd say if you can live without the creature comforts of a built-up camper, a simple fiberglass topper with a decent sleeping arrangement would be lighter, less expensive, and more flexible. It would allow you to get decent MPG and depending on how you build it, you can reconfigure or remove the sleeping/cooking platforms when you're at home to use the truck as a truck (hauling lumber, firewood, etc.)
IMO, if you absolutely have to have a cabover camper, then you need a full sized truck.