Well, the inboard mount (#3) certainly looks like the stock location, and so does #2, if memory serves from working under the seat of my early '71. I have no idea why there'd be no mount on the other side--maybe '67 was before rear seat belts were required, kind of like the B- and C-pillar mounts that were added during the production run.

You said you had a reel mounted at #1? A '67, if it even had shoulder belts, wouldn't have come from the factory with retractable belts. They would have been the non-retractable type that hold you really well but make adjusting for different drivers really frustrating and reaching the dash switches almost impossible if you're short (I'm 5'7"). Is the pivot for your front belts under the rear quarter window?

If someone retrofit reels to mount under the seat there, that's a different idea than I've seen before. I followed Mike Self's advice and put reels on the riser under the front of the rear seat when I retrofit retractable belts in my car. I could send a picture in a month or so when I'm back in the States.

-Dave
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Colorado '71