My '71 has the same arrangement. But in mine, the wire moves freely through the hole in the drum; it's kept in place by the number of turns around the drum. If yours is stuck, about the only thing I could suggest is soaking it in solvent to try to get the guts inside the drum to move. If that doesn't work, you may have to drill it out.
Chris Crighton
s/v Squander
T34C # 180