I had a cracked head. After i changed it i put the original thermostat bracket back on. The one on the Right. and i ended up breaking it. So i put the one that i pulled off a 89 cherokee. That is the one installed in the picture, on the Left. But as you can see there is no spot for that electric plug....
my question is, what does that plug do. can i live without it?

 

I wouldn't suggest it. That's the sensor that turns your auxiliary fan on and off (it may replace the ECU sensor as well - I'd have to look it up.)

There are two thermostat "housings" in use on the 242ci I6 - the one installed in your picture was used from 1987-1990. The loose one with the sensor in it is the 1991-2006 housing - and should be pretty easy to find a replacement for (easier than my RENIX, and I can get those just for the asking.)

Get one for any Jeep, 1991-2006, using the 242ci/4.0L I6. That port didn't change all the way up - it's threaded 3/8" NPT. Install the new housing, move your sensor over, and refill. Problem solved.