if you need/want a tach just swap in a Expo or Ranger gauge cluster that has a tach. There are some nice ones like the Sport Trac, Expo Sport, FX4 LII, and others that have cool colors and stuff.
Here is mine:
It's a 01 Sport Trac 2WD cluster with a Ranger cover. The Sport Trac one is silver instead of black around the white.
I think I paid $50 for it but I only paid $30 for my standard Ranger one I had before. They pop right in. No mods required, takes like 20 minutes if you've taken your dash apart before. Like 45 if not.