According to Helm, Inc, it's GMP06M for the '06.

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Deep, steel/sand, loaded except standard radio and no smoker's; #08974
Mods: Kappasphere CAI, Clear Image Shorty Header, second horn, visor decals, mudflaps, tonneau cover, brake light flasher, trailer hitch, 'lil Chromies, trunk monkey, retune, DDMWorks backbone, GMPP Suspension