Tail light stays on

"All the time?" You mean when parked with all other power off? What do you do to keep the battery from going dead?

If the above is true, part of the harness must be crossed/ shorted to something live. The only thing in the rear harness that would be live is the feed for the trunk lamp

If so, pull the rear seat and look for a pinch in the harness. If not, pull the carpet/ left kick panel until you can access the harness and inspect it. There's a connector in the left kick panel to separate the rear harness. Separate that and probe that connector to see if power is being fed to the tail circuit from somewhere "ahead."

You can download wiring diagrams and service manuals from MyMopar. some of the manuals over there came from the guys right here, including TB