The only advice I can offer on that one is to route the cable through the firewall and attach it to the speedo head FIRST. When you do it this way it allows you to pull the cluster further out of the dash while you are putting it together and therefore it is easier to do. With it connected at the speedo end you have it routed down to the trans where you pull up the slack and attach it to the speedo drive gear and you are done. The connection back at the trans is relatively wide open and easy to get to when compared to the connection on the back of the instrument cluster.

Mark