66 Barracuda /6 auto, has a tach??

I might be picking this car up sometime soon, and I was just wondering what is up with it. It's a 66 Barracuda, /6 auto on the column. It appears to have a factory tach in the dash. Any reason? It's an automatic /6 car.. I thought a tach would really only come on say a Formula S Commando car? Or is it just some sort of performance indicator? Teach me!