GMPartsGiant.com offers the wholesale prices for genuine 2018 GMC Sierra 2500 HD 4WD parts. Parts like Paint/Touch-Up 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: 2500 CREW CAB STANDARD BOX, 2500 REGULAR CAB, CREW CAB 2500 LONG BOX, DOUBLE CAB 2500 LONG BOX, DOUBLE CAB 2500 STANDARD BOX.