Buckling up a seatbelt has become second nature to us and I feel very unsafe riding in any car without one, especially when my face is just inches from the windshield, hard dashboard and non-impact absorbing steering column. Therefore I installed 3-point belts in my Fordor.
The lap belts are attached to brackets that are anchored through the floor to an angle iron bar spanning between the frame rails, basically as others have mentioned above.
The big problem of course is how to attach the shoulder belt to a wood frame with no holding strength? I'll try my best to explain. My solution was to attach angle iron brackets that sit on and are screwed to the wood rail just above the door posts. The shoulder belt is bolted to a nut welded to this bracket. Another steel bar runs across the roof, above the headliner, and is welded to each bracket. This keeps the whole assembly in place and hidden. With this arrangement the pulling force of the shoulder belt is directed downwards and forward through the door post and frame. Imagine someone jumping on the roof and pushing down.
Will this hold up in a 45 mph front end collision? Obviously not, but neither will the car or its occupants, but at least it provides an increased level of safety over lap belts alone and I feel much more comfortable driving now with all the crazy drivers on the roads. I've tried to add a picture of the attachment, but not sure if it will work...
