The box was done by previous owner , cant help on cost. But if your in the portland area and want to copy it. just holler..........
There are two recievers on each side welded to the frame and the box is capable of sliding on and off. The bumper is bolted to the frame under the recievers. The spare tire is sitting on the bumper and is bolted into the box which is locked. I even carry a white water kayak on top of the box and have had no problem...................works fine.