Modern Seat Belts?

Great thread, I want/need to do this.
I saw a 74 Swinger last night that had shoulder belts, attached to the floor near the seat, and in between the rear seat and the rear panel.

Would these fit earlier a bodies?

Does anyone know if the 67 Barracuda has the roof mount?
I'm finding that 68s look very similar, but there are many, many, differences.