Shop Manual to the rescue!
Clock Assembly --- Removal
1. Disconnect negative cable at battery
2. Loosen set screw securing clock housing to cluster bezel, using a 5/64 inch Allen wrench, Fig 15-3. (shows position of set screw beneath 6 o'clock as Alan pointed out)
3. Carefully lift upward on bottom of clock housing to disengage upper retainer clip from locating slot in cluster bezel opening, then pull clock assembly straight out to remove.
4. Disconnect clock feed wire and two clock dial bulb sockets from housing case, and remove clock assembly.
Gotta love those shop manuals!
Geoff N.