Parts in approximate location. The receiver end is centrally mounted to the cross sill behind the tool pan. There is a doubler plate welded under the sill, which has a 1/2-20 grade 8 nut TIG welded to it. A grade 8 bolt and washer goes through from the top.
There is also a doubler plate and nut TIG welded under the outboard side rail. There is an angle bracket made from 3/4 OD 0.060 wall tubing flattened and with 1/2 inch holes drilled in it. The tubing bracket is bolted to the sill and to the retractor as shown in the next pic.
Belt and retractor bolted in position. The retractor is mounted outboard on an angle with the retractor body in the cavity inside the quarter outer panel, just behind the end of the side upholstery trim panel.
With the seat installed, the retractor does not foul the upholstery or the seat movement, and the belt tongue is placed in a convenient place where it won't get slammed in the door.
The taupe colored belts are Allied Signal model 1560. All hardware is 1/2-20 grade 8.