Thanks Paul. Its been fun, and that's the main thing. Although tonight I hit a snag. The GPS Speedo I purchased to replace the Z3 speedo, was meant to have adjustable mileage. It hasn't. There is a grommet which when removed should reveal a momentary switch. But its isn't there. I have stripped it down to see if I can bridge the connections on the gauge's PCB, just to set the mileage ... alas no. I've already wrote a disgruntled message to the ebay seller.
I now have 2 choices ...
- Purchase another GPS unit and hope the 'adjustable mileage' button is present and it works (although the last one took a couple of weeks to arrive)
- Buy an old Smiths speedo, fit the Z3 workings in that. But this would mean I would have to display the original Z3 LCD somewhere (probably too big to insert inside the speedo, width/height wise). Also, this involves extending approximately 40 pins from the PCB to the new dash
It can be done, but it's more work. I might be able to use an old 40 pin IDE ribbon cable out of a PC.
Either way, there's no going back now
I'll sleep on it (if that's possible in this heat) and see what tomorrow brings.