Nice work...I've been trying to come up with a similar solution for my bus. I plan on using VDO style senders to an Arduino and then digital potentiometers on the output of the Arduino to make the gauges on the original dash work.
I'm going to give your little project a go though...I've got 3 Empty gauge holes that need filling in my Supra and those can-bus ones are really parking expensive!
Incase you're curious, the arduino project of mine can be found here:
https://github.com/hotswapster/bedford330
It will also have stuff you can use on other vehicles swell.
