In 72, the Challenger Rallye had a JS VIN. The standard Challengers had a JH VIN. 72 is the last year that the JS VIN was used. In 73 and 74 ALL Challengers had the JH VIN and the Rallye was just a package option on the base Challenger. If a 73 or 74 is a "Rallye" it will have A57 on the fender tag. That is the code for the "Rallye Package".
This is why I think the tail panels became standard for all Challengers in 73 and 74. 72 was the only year that the Rallye was it's own model. The factory was also starting to try and save money by making parts fit multiple vehicles and years. (72-74 E-bodies went mostly unchanged, side markers were standardised, fender mount turn signals were standardised in 73, 73-74 Challengers used the Cuda vinyl tops, door handles were changed so they would work on both Challengers and Cudas exc...) 73 is also when the thick bumper fillers started. They would have had to stock two different tail light housings as well as two different styles of filler panels.(filler panels are painted argent too)
