1970 Ford Mustang Ring and Pinion Set Ford 9 in. - Ring and Pinion Set - 3.89 Ratio - 9310 Pro Gear - Oversized 35 Spline Pinion - Rear guaranteed to replace your current 1970 Ford Mustang Ring and Pinion Set Ford 9 in. - Ring and Pinion Set - 3.89 Ratio - 9310 Pro Gear - Oversized 35 Spline Pinion - Rear. 1970 Ford Mustang Ring and Pinion Set comes new OEM 1970 Ford Mustang Ring and Pinion Set aftermarket new 1970 Ford Mustang Ring and Pinion Set of remanufactured 1970 Ford Mustang Ring and Pinion Set Ford 9 in. - Ring and Pinion Set - 3.89 Ratio - 9310 Pro Gear - Oversized 35 Spline Pinion - Rear.