This is verbatim current federal law (49 CFR 565), I'm sure it was similar in 1968
"The VIN for passenger cars, multipurpose passenger vehicles, low speed vehicles, and trucks of 4536 kg or less GVWR shall be located inside the passenger compartment. It shall be readable, without moving any part of the vehicle, through the vehicle glazing under daylight lighting conditions by an observer having 20/20 vision (Snellen) whose eye-point is located outside the vehicle adjacent to the left windshield pillar."
Basically says all cars must have a clearly visible VIN seen through the driver's side windshield. Federal law supersedes state law.
Maybe not similar or even there?
§ 565.2 Application.
(a)(1) Except as provided in paragraph (a)(2) of this section, subpart B of this part 565 applies to passenger cars, multipurpose passenger vehicles, trucks, buses, trailers (including trailer kits), incomplete vehicles, low speed vehicles, and motorcycles manufactured on or after October 27, 2008 whose VINs have a letter “A” or “B” in the 10th position,
and to passenger cars, multipurpose passenger vehicles, trucks, buses, trailers (including trailer kits), incomplete vehicles, low speed vehicles, and motorcycles manufactured on or after April 30, 2009. Vehicles imported into the United States under 49 CFR 591.5(f), other than by the corporation responsible for the assembly of that vehicle or a subsidiary of such a corporation, are excluded from requirements of §§565.13(b), 565.13(c), 565.13(g), 565.13(h), 565.14 and 565.15.
(2)
All motor vehicles identified as model year 2009 or earlier vehicles by their manufacturer must comply with subpart C of this part 565
(subpart C appears to only affect cars back to 1980, see wiki quote-adriver)
(b) Subpart B of this part 565 applies to vehicles manufactured on or after April 30, 2008 and before April 30, 2009, whose vehicle identification number (VIN) does not have a letter “A” or “B” in the 10th position of the VIN and that are not identified as model year 2009 or earlier vehicles by their manufacturer.
[73 FR 28370, May 16, 2008]
[73 FR 23379, Apr. 30, 2008, as amended at 73 FR 28371, May 16, 2008]
http://www.vintageautomotive.net/?tag=vin-tampering
In the United States, the
National Traffic and Motor Vehicle Safety Act of 1966
(effective January 1, 1968) mandated certain safety requirements on vehicles to be sold in the USA such as side marker lights, safety belts and Vehicle Identification Numbers (VIN) visible on the dash through the windshield.
(not CFR 565 then?)
http://en.wikipedia.org/wiki/Vehicle_identification_number
From 1954 to 1981, there was no accepted standard for these numbers, so different manufacturers used different formats.
In 1981, the National Highway Traffic Safety Administration of the United States standardized the format.[1] It required all over-the-road-vehicles sold to contain a 17-character VIN, which does not include the letters I (i), O (o), or Q (q) (to avoid confusion with numerals 1 and 0).
http://www.martiauto.com/faqfocus.cfm?qid=245
If you encounter a DMV agent who starts questioning your car because of that, have his/her supervisor called immediately and point this out. I have known of overzealous agents who impounded the vehicle and removed the "offending" tag. It was replaced by a state-assigned VIN. This will affect the value of your vehicle (and I don't mean positively).
