Richmond 3.90 Ratio Ring and Pinion 30 Spline Pinion 8.500" Ring Gear 3 Series - GM 12 Bolt Hose Cover Calibration Plug:

Calibration Plug:

1966-1968 Mercury Commuter

Black Only

140 lb/in Spring Rate

gasket seat * Recommended spark plugs are Champion RC12YC or equivalent 14mm x 3/4" reach with flat gasket seat

Richmond 3.90 Ratio Ring and Pinion 30 Spline Pinion 8.500" Ring Gear 3 Series - GM 12 Bolt Hose Cover Calibration Plug:Product Description: Ring and Pinion 3. 90 Ratio 30 Spline Pinion 3 Series Thick Gear 8. 5 in GM 12 Bolt Richmond Gear is famed for their tough and reliable ring and pinion sets. That same level of reliability and precision is available in their other driveline products, including differentials, racing Transmissions, driveshaft components, and more. Racecars around the world rely on Richmond premium gearsets and Transmissions; your hotrod will run