If its an aftermarket tach, they've usually had a 3 position switch for use on a 4,6,8 cyl engine. I've never been swanky enough to have an in-cluster aftermarket, but I would assume they would have the same arrangement. The newer stuff might have a soft key button rather than a physical switch, and/or maybe even a connection to set with a laptop or something. if you see a brand name anywhere Google to see what they offer even if you can't find a model #