The M5 used to run on 57th Street instead of Central Park South. IIRC, this was changed the same day as the other 57th Street changes, which I outlined in my earlier post.
The M7 has always (i.e., as long as I can remember) used Central Park South westbound (northbound), to Broadway, as it does today. Until the late 80's or early 90's, the southbound M7 continued down Columbus past 64th, turned left on 58th, and either ran across 58th to 7th or turned left at 8th, right at Columbus Circle, right at CPS, right at 7th (yes, that means the southbound route ran north for about half a block) -- I think it flipped back and forth between these a few times before being ultimately routed down Broadway to CC instead.