It was my understanding that in most states the only time you have to wear seatbelts in a pre '66 vehicle is if either they were:
a. factory installed
b. installed aftermarket
And the only time you'd have to have a second taillight working in a pre 60 vehicle is if it was either:
a. factory installed
b. installed aftermarket
So if you just added turn signals and tail lights, you wouldn't have to put in seatbelts, or if you put a seatbelt in an old truck, you weren't required to upgrade EVERYTHING to current DOT specs.
If that was the case, then folks would be getting tickes for all sorts of things.. like not having saftey glass installed.
Commercial vehicles, however seem to have to follow a whole different set of rules.
