if i can find the place where it lives theres a guy that did this to a 93? explorer. he cut the body off right behind the doors and somehow put the rear end of a ranger cab on it. it also has about 2.5" of the ranger box on it with the tailgate!
There is a guy around town who run's a Ford Focus pick-up. I t was a four door wagon that he sealed off the two front doors and made the rest a truck bed. Calls it the Foc-up. Never could get a picture..
A guy on RPS tired to do something similar to this, but he ended up scrapping the idea. Personally it would probably be cheaper to buy an over seas Ranger or from another country that has the 4 door models and shipping it here.