If I recall correctly, and it will take an older member to substantiate it (or someone with the appropriate map), I seem to remember taking an M72 that traversed Central Park via Terrace Drive for an exit at West 72nd when I was a wee lad in the late 70's/early 80's.
The best I can find to confirm that, or show I'm finally losing it, is the '74 and '76 maps, which show no such route. However, it might have been a bit later when the trip(s) happened. Of course, it might be sticking in my mind that it was an obvious deviation from the normal route...but then again, I know my mom didn't drag me over to the west side too often either (Oh, it's much improved since those days).
Anyhow, it was a nagging local mystery (of my own), and no, I'm not mixing it up with the M79.