obviously a short but does anyone have any light on the subject? where harness runs where it might not be protected. where i should look. thanks!

Check the insides of the bulb sockets for corrosion and clean them. remove the rubber boot on the back of the socket. Pull the metal bulb receptacle out of the plastic piece, and you will expose the ground wire, If it's corroded, clean it, or cut and strip a new sectioin. Reinstall the receptacle with the wire contacting the metal in a different point.

Have you done anything with the tail lights recently? Sometimes you can crush wires when putting lights back in..