1966 GMC I2500 4.1L 6 Cyl GAS. 1965 GMC I2500 3.8L 6 Cyl GAS. Notes: Radiator Cap/Cooling System Tester Adapter -- System adapter on tester. Ensure Proper FitTo confirm that this part fits your vehicle, enter your vehicle's Year, Make, Model, Trim and Engine in the Compatibility Table.
