The connector is on the backside (firewall) side of the cluster. Once the cluster is unbolted, gently wiggle it free from the metal dash and reach behind it to unplug the speedometer cable & electrical plug.
If you type "cluster removal" in the search box on this site it goes into a little more detail on how to remove it.
Just go slow & be gentle with it, remember that's it's 42 year plastic that your working with.