I made my own mount point while I had the headliner out. You can see where I put it here.
The Flying Valiant: Shoulder Mount Belt Reference
I used the lower lap belt locations and a non-retractable belt. I wanted to do retractable belts, but the problem is you need to move the retractor mount back to a new hole if you're gonna use it because it blocks the seat rolling back. I didn't want to drill more holes in the floor, so I went with non-retractables. It's fine, I wish I'd mounted it lower in the post because the geometry necessitates a strap pad so you don't get belt rash on your neck. I know it doesn't really protect against whiplash, but my main point was to keep from bashing my wife's brains out on the all steel dash in a front impact.