‘64 Dart Three Point Seatbelt Help

In 1966 Chrysler showed shoulder harnesses as a dealer installed option, but, I've never seen one that they installed. I wonder if they went to all the trouble of removing the headliner and welding in a plate on a hardtop. A post car looks to be a bit easier, but, I've never seen one of those done either.

I got it mostly installed yesterday. The welding on the B pillar is all i have left. Getting the retractor to fit with my seats and still go into a good mounting hole was tricky, and I’ll hav to start all over when i replace my floor pans and carpet.

I thought about removing my headliner to get in the b pillar but I don’t believe it would have worked, or necessarily hold better