I'm thinking they are model year specific. I believe the grilles on the 10-12's are a little different than the 13-14's. You could always contact the manufacturer and ask them though, if you know who makes them.
I know the ones listed on American Muscle have them listed for the two different body styles.
2012 GT Premium, Brembo Package, M6
VMP Gen II S/C & Tune, GT500 Axle-Backs/Spoiler/Strut Mounts
Steeda Sports/Shocks/Struts, J&M PHB, GT/CS Chin, MMD Fog Deletes