GMPartsGiant.com offers the wholesale prices for genuine 2018 GMC Sierra 3500 HD Denali 2WD parts. Parts like Engine To Transmission Mounting 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: 3500 CREW CAB LONG BOX, 3500 CREW CAB ONLY, 3500 CREW CAB STANDARD BOX.