It is recorded by GM that the J65 brake was only originally offered on the "SS" model. It is noted by CRG that examples have been found of this option on non-"SS" cars. I just wanted to show the example of my 2nd month of production car, built in October of 1966, vehicle number 15,797 from the Norwood plant. It's an RS/SS 350 with four wheel drum brakes. The front drums have no part number cast into them but they are stamped with an SS where the part number should be. They do have a GM casting date I096. September 9th of 66.