Speedo Cable
67s have a screw on cable on both sides, the tranny and the speedo.
I had a broken speedo cable and could not find a new one, so I ended up getting a 68 speedo and a new cable. The cable broke within a few weeks, cheap plastic clip on to the speedo.
I ended up switching back to the correct speedo and finding a cable in a junkyard.
If you spin the back of the speedo with your hand the needle should move if it works.
There are a few tiny gears that work the trip, but the needle is driven right off of the cable.
I just took mine apart if you need pics, and a few others.