My 62 Savoy has factory seat belt mounts (I have NO idea why!). They are slightly u-shaped reinforcements with a nut welded on, spot welded to the floor. I'm using mine for the lap belt portion of my five point harness. (I have to add a flat plate reinforcement for the crotch strap, and the shoulder belts are bolted,to the roll bar). They look like this... (if the pic comes out....) Ten o'clock in the photo.
Edit: pretty sure that is a 7/16 bolt. I don't remember if it's coarse or fine thread. It IS grade eight, as is all my harness hardware.
2nd edit: roughly even with the rear edge of the door (2 door)
3rd edit: the other two reinforced thru bolts are two of four bolts for fiberglass bucket seat mount brackets
4th edit: the glass seat is solidly mounted to the roll bar, per nhra regs.
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