Yeah Staffo, I think you will need to take off your tank console, its just 3 screws and disconnect a couple of cables to remove the tacho and give it a measure.
The Acewell model I bought (2856) was slightly different from Keith’s (2853) and so the dimensions are slightly smaller on mine, the sites listed have the dimensions.
The 2856 Model Dimensions: 64mm x 40mm
Shown here:
http://www.acewell.co.uk/Acewell%20Speedometers/ACE-2xxx/ACE-2856.htm?action=full&id=18The 2853 Model Dimensions: 72mm dia x 58mm deep
Shown Here:
http://www.s3performance.com.au/acewell-c-1.html?osCsid=cc1t1m8huqegbbcrk8h1m3g7m4I bought the LED version but you cant run tank console lights and the LED warning lights at the same time cause you risk blowing the speedo due to the amount of power the neutral pulls, NO big deal really as the LED unlit just looks like stickers.
BOth Sites also have all the adapters.