I owned a 1974 C&C27 and I have raced against quite a few similar vintage C&C boats. I don't know the flush deck C&C 30 but I would be surprised if any C&C boats of that vintage had an anchor light at the top of the mast. My father's 1974 Viking 33 (designed by C&C) did not have one either. Back in those days we always used a storm lantern suspended from a jib halyard, tied near the middle of the foretriangle, as an anchor light. Originally these were oil burning but we switched to battery eventually.
As
@pgandw said, it's good to have a light lower down anyway so passing boats can see it easily. The light at the top of my 53' mast wouldn't be as noticeable to someone in a runabout ripping through at 20 knots.