GMPartsGiant.com offers the wholesale prices for genuine 2003 GMC Sierra 3500 2WD parts. Parts like Spark Plug Wiring 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 6.6L Diesel, 8 Cyl 8.1L. Model Code: 3500 CREW CAB, 3500 EXTENDED CAB.