GMPartsGiant.com offers the wholesale prices for genuine 2013 GMC Sierra 2500 HD Denali 2WD parts. Parts like Brake Electrical System are shipped directly from authorized GM dealers and backed by the manufacturer's warranty. Parts fit for the following vehicle options. Engine: 8 Cyl 6.0L, 8 Cyl 6.0L Flex, 8 Cyl 6.6L Diesel. Model Code: CREW CAB 6'6" BOX 3/4 TON.