Right. Not nice, but this happens sometimes. Some cars were delivered without the speaker, then the instrument cover is closed under the grille. Recently seen it on a 75 3.0 L.
You may open the small glove box, reach behind the cluster and unscrew and pull out the speedo cable from there. Possible if the nut on the cable is fastened like it should (not very tightly). Then you can try to tilt the cluster from behind so that the top will come out first. Usually that will not work, nearly impossible to reach there and apply force. Which will leave you to remove the lower part of the instrument panel cover, the one with the push buttons, and tilt the cluster out from below. The two multi-plugs can be pulled off with the cluster out. The (works) wiring is long enough.
Putting a soft cloth over the steering column will protect the cluster's screen and rim which are not very robust. For the same reason, please do not try helping the cluster out with a screwdriver or a hook. A friend suggests to put a little grease on the speedo cable before remounting. He has noticed usually there is none left.