GMPartsGiant.com offers the wholesale prices for genuine 2008 GMC Sierra 3500 HD 4WD parts. Parts like Seat Belts-Rear 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. Model Code: CREW CAB 1 TON, EXTENDED CAB 1 TON, EXTENDED CAB CHASSIS 1 TON 161.5, REGULAR CAB 1 TON, REGULAR CAB CHASSIS 1 TON 137.0, REGULAR CAB CHASSIS 1 TON 161.5.