I did basically the same with mine. For the outer belts, I followed
Deve’s installation but bolted the L bracket thru the floor instead of welding it. That is shown in the forth picture without the retractor (I installed 3 point belts, but the attachment points are the same). I used a 1-1/2” x 4” x 1/4” plate, which slid nicely under the cab attachment bracket to bolt the L bracket into.
The issue I ran into was routing the center belts thru the seat cushion frame. The belts would rub on the sharp edge of the seat frame. I remedied the issue by cutting slots for the belts to run thru. Instead of cutting rectangle slots, I cut slits that looked like a wide H with a cutoff wheel on a grinder and a Dremel with a cutoff wheel for the side cuts, and folded them over so they didn’t leave a sharp edge.
