The Chicago 500 which consisted of the playlist of the top 500 songs was that on WJMK? Did WIND back in the 70's do that for the memorial day weekend also? I don't recall WCFL or WLS doing that.
WJMK did do it almost every year and you're right about WIND doing a Top 500 also. I think they did it a couple of times and actually published a list around the mid 70s.