If you are close to Canton, Texas go to The Muffler Shop on Highway 64 Ask for Johnny or Chad 903-567-2691. They have every kind of box you could ever want for a truck bed
i bought boxes from a place called perfection equipment in oklahoma city boxes are built in sherman texas brand name is deuhtech not quite sure if that is spelled correct but the strongest best built factory made box there is out there cant beatem.
i gave $525 dollars for two 18x18x40 boxes there is some pictures of my rig on the shop talk thread rig building oklahoma style i am the red dodge with triple c welding on the side windows.