7 WEEK OLD LANDSCAPE TRUCK JUST FILLED AT GAS STATION. AFTER LEAVING GAS STATION, DRIVER HEARD DRAGGING SOUND. WHEN DRIVER PULLED OVER AND STOPPED, HE SAW BACK OF TRUCK ON FIRE. INVESTIGATION SHOWED THAT 3 OF 4 FUEL TANK-TO-FRAME BOLTS FELL OUT ALLOWING FUEL TANK TO DRAG ON GROUND. AFTERMARKET LANDSCAPE BED INSTALLED. FUEL TANK NOT REMOVED FOR INSTALLATION OF BED. PROBLEM APPEARS TO BE MANUFACTURER NOT PROPERLY INSTALLING FUEL TANK.*AK