1991 GMC Pick-up Truck Ring and Pinion Set K2500 - 4WD - GM 10.5 in Rear - w/ 14 Bolt Cover - 3.21 Ratio - Ring and Pinion Set - Fits 3 series 4.10 & Down Carrier - Rear guaranteed to replace your current 1991 GMC Pick-up Truck Ring and Pinion Set K2500 - 4WD - GM 10.5 in Rear - w/ 14 Bolt Cover - 3.21 Ratio - Ring and Pinion Set - Fits 3 series 4.10 & Down Carrier - Rear. 1991 GMC Pick-up Truck Ring and Pinion Set comes new OEM 1991 GMC Pick-up Truck Ring and Pinion Set aftermarket new 1991 GMC Pick-up Truck Ring and Pinion Set of remanufactured 1991 GMC Pick-up Truck Ring and Pinion Set K2500 - 4WD - GM 10.5 in Rear - w/ 14 Bolt Cover - 3.21 Ratio - Ring and Pinion Set - Fits 3 series 4.10 & Down Carrier - Rear.