I'm interested in buying a pickup and the dealer has it listed as a Denali but the grill doesn't match the known Denali grill so I'm just wondering if GMC even made the Denali in a 2500 in 2003?
No, the first year for the Denali trim level on the 2500 series trucks was this years model, 2011. The 1500 series Sierra Denali became available in 2002. In 2001 it was called the Sierra 1500 C3.