Custom speedo cables and calibration

[mat_the_cat]

I'm trying to get the speedo in the Stellar sorted out, so am after any advice that might be around. Basically, I have two issues - connecting the Hyundai speedo to the R380 gearbox, and then calibrating it so it reads correctly with the higher ratio rear axle. I've contacted Speedy Cables but as yet no response. Richfield Speedograph are next on the list, but there is a plan C...

 

The gearbox can also be fitted with an electronic speed sensor, which opens up the possibility of using this:

http://www.abbott-tach.com/cablex.htm

 

Pricey, but I don't yet know how that compares to the purely mechanical option. I can see how a cable could be made up to fit both ends but to recalibrate the speedo does someone need to construct a tiny gearbox to fit in the cable? I really want it all to look original, at least on the surface so the idea of just using a sat nav doesn't appeal although I may have to do that temporarily.

 

Anyone else been in the same position?