Seeing how the fixing works in principle is a great help. .A T piece spanning the location Holes ,plus a piece extending to a fixing point on the seat runner . Having measurements helps if you want to fabricate a T shaped replica without reference to the car and mat, and manage to get the positionings accurate.
But I'd have said its a much simpler diy job to simply lay a strip of metal or heavy duty plastic,maybe an inch or 3cm wide, between the two holes on the carpet, and use these as a template to drill two holes in strip to install the fixing posts . The posts could be self tapping screws, or small bolts with the carpet secured by nuts,maybe wing nuts.
Then drill a hole near the end of a similar strip for fixing to the seat runner, and with the car mat in position with its strip, mark where the strips cross as a T, and drill a hole in both to fix them together. Simpler to make and using the actual car and mat as an accurate template. The principle could be adapted to other cars and other brands of mat.
I dont think the fixing studs need to be particularly sturdy. The studs on my Mk 4 are plastic and attached solely by sliding through pre cut slots in the factory fitted carpeting .. Its just the carpet that holds the studs in position, not sturdy metal plates. Maybe with some ingenuity this same method could be adapted for the mk1.
