I'm having a hard time following your though process here. When you purchase a weight distribution system, you get the bars, the parts that connect the bars to the trailer tongue. You get the hitch head that the other end of the bars connect into and the shaft the hitch head is is connected to. You then get a new ball that matches the weight you are towing, (or heavier). In other words, the weight distribution system is a complete set.
Correct me if I am wrong, but it sound like you want to use parts between the two weight distribution systems inter changeable. I know nothing about the "S" you are referring to, but I almost guarantee the Reese Dual Cam will not have inter changeable parts.
Get the entire system for your camper, keep the other system for the horse trailer. Keep it simple. Use them the way they were designed, and keep everything safe as possible.
Good luck in your choice.