Hi 'debbie 100', it turns out that I had already run the wires to the back of the car before I saw your post. I cut into the wires going to the stop and running lights in the tail light assembly, and the RV actuates these lights through the Roadmaster diodes I also installed. It has worked out fine so far - but if I had known, I would have probably bought the Roadmaster kit that you have. Thanks anyway!
P.S. I purchased a Brake Buddy module for the remote braking, which also works well :-)