1966 GMC Pick-up Truck Ring and Pinion Set K15/K1500 Pickup - GM 12 Bolt Truck - Ring and Pinion Set - 5.13 Ratio - Fits 4 series 3.73 & Up Carrier - Rear guaranteed to replace your current 1966 GMC Pick-up Truck Ring and Pinion Set K15/K1500 Pickup - GM 12 Bolt Truck - Ring and Pinion Set - 5.13 Ratio - Fits 4 series 3.73 & Up Carrier - Rear. 1966 GMC Pick-up Truck Ring and Pinion Set comes new OEM 1966 GMC Pick-up Truck Ring and Pinion Set aftermarket new 1966 GMC Pick-up Truck Ring and Pinion Set of remanufactured 1966 GMC Pick-up Truck Ring and Pinion Set K15/K1500 Pickup - GM 12 Bolt Truck - Ring and Pinion Set - 5.13 Ratio - Fits 4 series 3.73 & Up Carrier - Rear.