Shoulder belt issue on 68 Barracuda

SGBARRACUDA said
That would be a good fix, except for the fact the headliner is installed, the carpet, seat belts rear seats ,etc are in the car all ready. Thanks

That was my predicament. I did it per my photos and used a marine grade two part epoxy to bond the washer to the car upon installation.
Can be done but takes patience and flexibility.