Help

I have a 1972 AMC Hornet. I need to replace the wheel cylinders on the front. I went to a part store and they looked up the part. When he brought the part out it was not the same as the one I took off. He assured me that it was the right one according to the computer. He checke every AMC model for 72,73 and 74. None of them matched. Has anyone any idea what kind o brakes AMC put on this car. This is my first AMC car. A friend told me that this was not unusual for AMC. If they ran short, AMC would buy from other Manufacturers.