Just re-thinking at which point they may have put the FMVSS/CMVSS label on with the MDH info.....possibly when they installed the last component regulated by the Federal Motor Vehicle Safety Standards on the car so they knew which cars they might be ordered by the Feds to recall. Could have been the wheels and tires, the wipers, or whatever was in these regs as of 1973 (I think up to FMVSS 214 back then).

Take a look at PART 566 and then PART 567 kind of goes with the GVWR on the label in the bulletin you posted.

http://www.nhtsa.gov/cars/rules/import/FMVSS/index.html#SN202