Each side light has two wires going to it. White wire seems to terminate at the ball. If I want to run a separate neutral/ground what would I hook it up to at the light end. Each light has two terminals - where would I attach the white?
The ground connection is the lamp housing. I'd put a ring terminal on your new ground wire and put the terminal between the head of the bolt and the housing.
Added: Automotive (trailer) wiring is suspect to corrosion. Get the shrink style ring terminals.
What we've got here is... failure to communicate. Some men you just can't reach. So you get what we had here last week, which is the way he wants it... well, he gets it.