GMPartsGiant.com offers the wholesale prices for genuine 2018 GMC Sierra 1500 4WD parts. Parts like Audio System/Rear 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 5.3L, 8 Cyl 6.2L. Model Code: 1500 CREW CAB STANDARD BOX, 1500 DOUBLE CAB STANDARD BOX, 1500 REGULAR CAB LONG BOX, 1500 REGULAR CAB STANDARD BOX, CREW CAB 1/2 TON.