You're supposed to disconnect the cable from below. Don't ask me how though - I tried removing my cluster once (there's dust in it & I wanted to clean it) and I eventually gave up.
In case you don't have a copy, the service manual says:
The instrument cluster is held in place by means of
five spring clips located on instrument panel.
1 Remove cover under instrument panel, left.
2 Remove hose (arrow) toward lefthand lateral nozzle
from below.
3 Unscrew tachometer shaft on instrument cluster
from below.
4 Push out instrument cluster from the rear.
5 Disconnect electrical connections and line for oil
pressure gauge, remove instrument cluster.
If you figure out how to remove it, let me know!
