GMPartsGiant.com offers the wholesale prices for genuine 1999 Chevrolet Silverado 2500 4WD parts. Parts like Wiring Harness/Auxiliary are shipped directly from authorized GM dealers and backed by the manufacturer's warranty. Parts fit for the following vehicle options. Engine: 8 Cyl 5.3L, 8 Cyl 6.0L. Model Code: 2500 EXTENDED CAB LONG BOX, 2500 EXTENDED CAB STANDARD BOX, 2500 REGULAR CAB.