I have seen portions of the body style written on the firewalls, like "10734" written with a grease pencil.
I also learned that FoMoCo (for instance) had a VIN tag mounted on the Passenger side of the dash between the pad and the windshield, in '68. I don't know if the other MFR's did that then, or not. I was overseas and had nothing but a Honda 90 and a wish list a mile long.....
I'm going to bet at some point in the future, there will be a question on here about their VIN tag not having a Bar Code.....