Some coupe owners in the past have asked about the rectractable seat belt conversion from the 74 US coupes. Don't know if the 74 and beyond Euro coupes also have this seat belt assembly. Here is the setup on my 72 CSi. The hook is for "hanging" of the belt only and offers no structural support so belts need to be "unhooked" during use. The single mounting hole for the belt reel assembly should be on the car already therefore no modification should be necessary.
Bert
72 3.5 CSi
88 M6
Bert
72 3.5 CSi
88 M6