Nice writeup.
For the sake of those who may read this thread down the line, I'll post two additional thoughts:
First, when removing the instrument cluster ("IC") from 107s, a critical ground is sometimes, for no apparent reason, lost. If you get everything back together and then notice that your gauges are dancing all over the place, especially when the turn signals are activated, or if other untoward things are happening, then you have most likely lost that ground.
After the initial heart failure recedes, you have two options. The first is to track down this grounding problem, which can take hours, days, months, years, a lifetime, etc. The second, and by far better, option is to simply connect a new jumper grounding wire between the IC (use one of the screws on one of the metal backing plates of one of the three pods) and a good chassis grounding point behind the IC. Splice in a quick connect so you can remove the IC again without having to disconnect the jumper from its grounding points.
Second, for Speedo repair issues, try Rick Borth at Overseas speedometer in Austin,
http://www.speedometer.com/, 800-444-0292. Quality work, fast, reasonable.
Cheers.