shoulder belts in a non shoulder belt car

anyone install shoulder belts in a non shoulder belt car?
Wondering how much if any roof reinforcement would be required in a car like a second generation Barracuda that does not have a B pillar? For where the shoulder belt hangs above head height.

I currently have Chrysler Sebring seats installed, they have the shoulder harness built into the seat back, at some point in time I would like newer seats with more lateral support,,
If you can't find a good way to add the shoulder belt to the car, you can modify your existing seats to have more lateral support and then cut some custom foam.