Here's how the seat went in...
I was hoping someone would post some simple instructions I could follow, but you gave me Nothing. I did a quick internet search and looked thru my junk pile. Here's what I came up with:
Stripped a seat base from storage down to the rails and bolted on some cut pieces of slotted angle iron (1-1/2 x48" ) cut to 5" lengths. I would have preferred U-channel, or box, but this was the best choice for local availability and budget.
Bolt right seatbelt through angle iron.
Bolt a flat plate to the slotted angle iron. This piece came from a scrapped flat panel TV mount.
Drill holes in seat and mount to flat plate. I bolted through the seat and plate to the rails. The other holes were in the seat from the previous owner's install.
Covered with the harness installed.
***Note: This car is being built for an event with a $2,000 budget limit and for my own entertainment. Do not try this on your own car without first consulting a competent mechanic and some YouTube videos.