Does anyone know how in 1968 Pontiac started tracking the three major components in there GTO vehicles. Known as numbers matching, I'm aware that the last six characters of the vehicles VIN, were stamped into the engine block and the transmission installed at the time of the vehicle assembly. However, how did the manufacturer assure ' that particular rear end was part of the original drive train? I know Mopar and some GM products added a tag or a stamp to the rear end with the VIN characters post 67. Too identify the rear end as part of original build. This question has been a item of much heated debate.