Charger bumper brackets

[challenger6pak]

I have several front bumper bracket halves that came with a bunch of Charger parts. They have numbers on them but the numbers do not seem to be part numbers. I did notice that one set of frame holes is inline and another set is staggered. From what I have seen doing a internet search the inline is for 73 74 Charger. Staggered is for 71 72 . Is this correct? Thanks.

 

[challenger6pak]

I still have a bunch of these brackets I would like to identify and sell. How do I tell the year difference? Thanks.