Finding a used truck with the right configureation is going to be a headache. This F-350 is roughly in the ball park of what I'm looking for but the bed is wayyy to long and would need to be cut shorter so I could put a trailer hitch on back. From the looks of it the bed seems like it would hit the ground at full tilt.
http://washingtondc.craigslist.org/doc/cto/4167898782.html
http://washingtondc.craigslist.org/doc/cto/4167898782.html