Dan... I'm going to toss this in GH as well for a write up.
For this to work properly there is a dot on the inner collar by the selector shaft of the trans that must be lined up with a line on the body of the external switch. Dot is being pointed to in the picture
Once these are lined up. Put in the two bolts and tighten. Put the selector arm back in place and the nut that holds it to the shaft, tighten the nut. Connect your two new external range selector connectors and the main trans connector. Turn the car ignition switch to on and review the dash to see that the gear selection is now appearing.