Fram part # for Monte's and Impala's is CF8392 or CF8392A if you want the fancier one. fram.com will show you all of the competitors part #'s if you prefer another maker.
It did not show a cabin air filter for an 03 GP though. Strange. Does yours have one?
Here is a link for an 04 GP cabin filter install with pics, just to compare.
Sparky's Answers: 2004 Pontiac Grand Prix, Changing The Cabin Air Filter