I have a 1970 F100 and it has two lap belts that look original. I don't know if it ever had one in the middle, but I doubt it.
It seems that they were available as an option but did not come standard. Here is a link to a car that has them from the factory: http://home.pacbell.net/davriker/Wagon%20Web/my1963.htm
no
1971
Check your alternator belts. Might be slipping or broke.
come on! blue falcon!
Seat belts, yes.
a wool fabric
No, the 1957 Chevy didn't come with seat belts.
lap belts only lap belts only
a falcon
Not if they did not come from the factory with seat belts. If they came form the factory with seat belts you are required to wear them.