True, it only gets tighter going forward... although the frontal impact is most likely, at least on a street car.

I suspect another reason for having the seat and belts attached together is that it's quicker on the assembly line!

Anyhow I think I'm going to buy new shoulder/lap belts, manual adjust, that fit the original mounting points (on the floor and roof). 3" sounds like a good idea, to reduce the loading per unit area on my body...

I have never liked retractors since they eventually get "sticky", and I worry that they may not lock when I need them to. I ran a car off the road once at 55 mph and went through the median ditch, flew up in the air and hit my head fairly hard on the roof. The belt never locked with the vertical acceleration, so fat lot of good it did me for that impact!

Incidentally, is there any value to the old bench seats? The driver's spot is, of course, worn out, but the rest is OK. Maybe they should just go to the dump...