Gentlemen, the brake booster on my sons 72 skylark 455 has failed and I need to order a replacement. The car has drum brakes and that's what we are staying with. My question is, OPGI shows a booster available for drum brakes, but you have to specify 9" or 11" when ordering. From my measurements across the face of the booster it is about 10 1/2". Maybe I am measuring the booster in the wrong spot? I have to admit, I don't know which one to order. Can anyone point me in the right direction? Thanks guys
