The door side stationary point is the back of the seat pedestal. I used angle iron that was included in the kit that had an anchor bolt already included. I just welded it to the backside so the mechanism can sit on the floor just in the corner. It ended up working really well.

http://devestechnet.com/Images/Projects/SeatBelts/beltpic16lg.jpg

other pics on the install can be found here:

http://devestechnet.com/Home/SeatBelts

Deve

1950 Chevy 3100 Deluxe Cab
1950 Chevy 3100 Standard Cab
In the Stovebolt Gallery
The Think Tank
More info and tips at Deve's Technet