there may be a small flaw in your explanation. THE FEDERAL MOTOR VEHICLE SAFETY STANARDS ACT was in its infancy in 1969-1970 the description of #2 was written in 19999 for the year 2000, much like anything the government does gets updated continually ,probably to close the loop holes that the manufactures had found. in 1969 the first FMVSS decal was printed and ended up on some of the 1969 Daytona's. the first decal read "THIS VEHICLE CONFORMS TO ALL APPLICAL U.S.FEDERAL MOTOR VEHICLE SAFTEY STANARDS IN EFFECT ON THE DATE OF MANUFACTURE SHOWN ABOVE". To me this says that the vehicle manufactured complies to the STANDARDS THAT WERE IN EFFECT on the date shown above. you may think im splitting hairs but that is what it says, and by the following year the wording had changed and again after that.
which means to me That the vin number and vehicle were assembled according to the rules that were in effect on that date provided above.the regulations could have changed at any time as this was all new to the industry and shows what set of rules they followed as concerning to public safety.