Yeah nice start. That was where the factory dual battery setup went on the heavier pickups.
I had the same problem with the washer fluid. Before you buy any parts, you should be able to see the two hose connections from looking up from underneath. If you fill up the container with water, you should be able to see if its leaking out of one the hose connections and just run a new piece of tubing quickly for a buck or two. The one I had to replace ran up to a plastic double male ended connector along the top side of the fender.
Are you willing to share your future plans, or keeping this a surprise?