just wanted to get some opinions and preferences on how everyone sets up their Tachometers. like AutoMeter type ones.

When you install a New Tach (the ones that mounts to the dash) do you leave the origonal one hooked up, or do you disconnect it? or is it possible to have both working, like to splice into the wire to hook up the new Tach? this is something i haven't done yet, and i'm curious. Thanks
already posted this in Audio & Electronics, but no response.