That's the sensor for the computer. There should be one to the right of the distributor in the intake itself that screws in vertically instead of horizontally like the one you replaced. It'll have one wire attached. That's the one for the guage in the cluster.
I found the other sensor that you're referring to. I plan to pick it up today. Then I hope to have a working temp gauge. Now since I put the actual sensor in, that's in the pic, the check engine light is off. The thing runs better than it ever has.