Seat Belt Anchors
I've had a harness bar for many years. At first, I attached the shoulder straps to the bar itself. But several years ago, I decided to attach the straps to the firewall and run them over the bar to keep them at the correct height, relative to my shoulders. That's what a harness bar is intended to do. So I fabricated several Aluminum plates that sandwich the firewall and used these to attach the shoulder straps. The Al plates are 3/16" thick. On the inside of the car, I cut slots in the plates and rounded the edges of the metal and threaded the seat belt webs through the slots to anchor them.