I know this is a necro, but I finally got around to installing the kit and while I knew this was a ground I wasn't sure where to terminate it. The original post ground location description didn't make sense to me and I was looking way too far back. This ground location is pretty much behind the front bumper, accessible from below. I would say hope this helps others, but given this kit is no longer sold I doubt anyone will be installing these in the future.
See diagram attached.