GMPartsGiant.com offers the wholesale prices for genuine 2003 GMC Sierra 1500 HD 2WD parts. Parts like Automatic Transmission Oil Cooler Pipes are shipped directly from authorized GM dealers and backed by the manufacturer's warranty. Parts fit for the following vehicle options. Engine: 6 Cyl 4.3L, 8 Cyl 4.8L, 8 Cyl 5.3L, 8 Cyl 5.3L Flex, 8 Cyl 6.0L. Model Code: 1500 CREW CAB LONG BOX.