Here is how I added belts to my '37. The first picture is the rear upper cab where I added a steel box tube all the way around for support of the upper mounting point of the belts. The second picture is the lower retractor mounted through the seat frame and cab floor with reinforcements under the cab. The third is the buckle mount in the center behind the seat frame. It's mounted to a heavy steel tube bolted through the floor with reinforcing plates under the floor.
