GMPartsGiant.com offers the wholesale prices for genuine 2003 Chevrolet Silverado 3500 4WD 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, 3500 REGULAR CAB.