66 Barracuda Shoulder Belts

I've been quite interested in this for a long time also. Two safety items for me that I would love to implement are (a) shoulder belts and (b) some way to keep the seat backs locked upright. I'm already in the midst of rigging up a collapsible steering wheel column and I have the seats torn apart and welding up head rests from a Mustang vendor. I wonder about welding a bar in on the outer side of each side of the car towards the back seat and fabricating a movable lock, so that way a pin or a release could be used to lock/unlock the seats in place. I wonder if that could be a suitable place to bolt in seat belts, also.