I happened to get my hands to original KM/H gauge from 71 240z. I wonder how pain in the arse project it is to change the gauge? I'd love to make my Z as Euro as possible (also its easier to drive correct speed here with km/h gauge on) Do you have to calibrate it somehow or what?

I think the rate of the speedo is specified by a gear in/on the trans for the speedo cable that is replaceable and color-coded. I read about it somewhere a while back, maybe for calibrating different rear-end ratios. Hopefully someone else will chime in on this.

As for pulling the speedo, I just did the tach and it wasn't too bad (except for having to trim back the dash cover), but the speedo looked a bit harder to get to.

Keep us posted, eh?