Rebuilding a bench seat

How do the plastic seat belt retainers come apart where they go through the bench seat and, are they available of they break?
1969 Application


Edit: correction.

This shows that All Bench attach to the front.
(All bench seat applications) (View in circle X)

69 front seat belt bolts.JPG

I think they screw in from the bottom the buckets do. Replacements are available here and classic as well.

Photo is from buckets, I fabricated the metal angle bracket .

20240131_195755.jpg