All fixed! I was able to reattach the cable to the back of the speedometer last night. I had to remove the attachment at the bottom edge of the dash in order to get enough slack in the cable. I had to take the three indicator bulbs loose from the bottom of the speedometer in order to get enough room in there to get my hand far enough in there to turn the knurled attachment nut. Once I reattached the cable to the bottom of the dash I tested it and found that turning the knob clockwise (as instructed in the manual) makes it just click. Turning the knob counterclockwise catches the numbers so that they eventually all return to zero.
