GMPartsGiant.com offers the wholesale prices for genuine 1991 GMC Sonoma 4WD parts. Parts like Wiring Harness/Auxiliary Lamps are shipped directly from authorized GM dealers and backed by the manufacturer's warranty. Parts fit for the following vehicle options. Engine: 4 Cyl 2.5L, 6 Cyl 2.8L, 6 Cyl 4.3L. Model Code: PICKUP.