Speedometer Cable

And you are sure you got the connector on all the way and clipped with the cable inside the speedo drive?.

Did the speedo work previous to this?

Yep only thing that changed was be replacing the voltage regulator which as a bolt right next to the cable. Since the dash was missing a screw their is a hole in the dash for a single din radio I wouldn't be shocked if someone was behind the dash before and had the cable a little loose so when I pushed on it some while doing the VR swap it probably knocked it out.