New Tach Installation

I found were to mount and wire but how long would it roughly take for 2 guys to install a Tach.

Depends on where you wire it. My friend wired mine for me directly to the ECU, so with mounting and adjusting the tach into it's location, running the wires, and hiding them; took about 20 minutes. But if you take out the gauge cluster to get to the wire, then it will probably take 30-45 minutes.