I had a buddy that did it not too long ago, but he had a shop do it. It cost him just under $6k. If you have a TIG or decent stick welder, you could go to a salvage yard and pick up a section of frame (or fab it from scratch) and a long bed. Throw in new brake/fuel lines and a spool or two or wire and you could probably git'r'dun for $1-2k.
Hahai don't think i could ever spend that much money for and extra 1.5 ft of bed space, call me crazy:confused013: but thats a lot of money