[Jason in TX]

My 68C Cabriolet has wooden subrails and a tool pan under the seat tacked with tiny framing nails. I am NOT going to put a bolt and washer through that metal pan and think I will not fly out of the open car if I'm T-Boned.

I anchored a drivers side belt to the body mount bolt that holds the B pillar to the frame.
I anchroed a passengers side belt to the body mount bolt just behind the door on the passenger side.

My wife and I wear the lap belt together like a roller coaster ride or I cinch the belt tight when I ride alone. Without adding an additional crossmember under the car for the center mount to have two separate belts, this was the most sturdy way I could think of doing it in the stock configuration.

All sorts of other issues still remain. Hitting your head on the glass. Chest impalement by the steering wheel. (look at old crash photos. This is what gets you) Bashing your head on that dangerous windshield wiper knob that is like a spike facing you. A gas tank in your lap surrounded by electrical contacts. On and on.

Ultimately, these cars are not safe and if Ford built this car today it would SERIOUSLY get denied by the DOT. We are grandfathered in and it's like riding a motorcycle. You just hope that another person doesn't hit you and whatever measures you've taken to be safe ultimately protect your life.