Cut out a hole in the dash and fitted a tachometer. I'm interested to know what it's doing when screaming at 100km/h on the highway.

Marked out where it's going to go.

Drilled lots of little holes. Cheaper than a holesaw.

Enlarged the holes with a bigger drill bit till it cut the majority out.

Using the dremel, grind away so it's smooth and round.

One more hole in the dash.

Fits nicely, looks neat.

Wire up to the coil.

Wahoo it works!