63 Valiant seat belt mountings

I looked for existing threads first but couldn't find this info.
I'm doing some general repairs on my friend's very rusty Valiant.
Next is seat belts.
He had a shop install some years ago, but they just drilled a hole through the floor, put in a big washer, and that's all.
Now, on the driver's side, by the door, the floor is rotted away and the belt is more or less only attached to carpet.
I don't know if Mopar originally had mounting points installed in all 63 Valiants.
I know my parents' came with belts when new. I'd like to attach the belt to the side frame, but before tearing out trim and carpet, I'm hoping someone can tell me if that was the factory attachment point, and whether I'm likely to find a dimple there, a plugged hole or what.
I wouldn't expect the floor pan to be a safe mounting point for belts anyway, even when the metal was new.
If someone has a 63 with factory belts, I'd appreciate a picture of the mounting point relative to the door and floor on the driver's side.
Thanks