I have been reading thru the posts trying to understand what type of spring is required for my car. Based on what I have calculated with the GM Spring Chart. I think my car, Z28, no special exhaust, no power steering, no spoilers, no RS would be a YF coded spring. Now the tricky part. Seems the Moog 6308s that everyone likes are not available. Springs in general seem to be hard to find. But I have a lead on an original used set. But I am trying to figure out how I would tell if they are the right ones for my car. So from the subject. Are there physical differences, markings other than the tags that would indicate which of the 3 options this used set might be?