Don,
As Jason described in post number 2 above, "the buzzer relay is mounted up in the dash by the steering column, on the same bracket as the cruise control unit". I accessed the relay on my '91 350 SD by removing the panel under the steering column. There was no need to remove the instrument cluster. It also helps if you have an eye loupe or magnifier to inspect the traces on the circuit board once you get it open. Good Luck.
Greg