For expediency, I fitted the complete St4s clocks to my 888. Ideally, I’d like to refit the 888 clocks with a white faced electronic tacho. I also have an old 750ss mount I could alter, the St4s tacho just about squeezes into the space. I don’t really want to butcher my 888 mount. The St4s clocks work, but the speedo is not calibrated properly for the 888 drive and they don’t look right. The clock is useful though!
Why don't you just have the tacho face plate changed to white, there are a number of specialists who can do this for you. https://speedycables.com/instruments/gauge-repairs-conversions/ https://www.motorcycleid.com/sport-bike/universal-dashboard-gauges/?vehicle=131769 http://www.guagerepairs.com/
you could use an electronic tacho from a guzzi daytona. Same as the tacho of the 851/888 but electronic and redline & 8000 rpm iirc. So this tacho will fit in your original 888 cluster
