Rob, after seeing what mine did I would HIGHLY recommend every Mustang driver do preventative maintenance and install the upper and lower kit before anything goes bad. I know this is not currently in the rules but it needs to be.

Richard is correct in every kit I've seen has some form of bracketry / welding done inside the car.

The kit I have in transit right now has interior brackets and I'm pretty certain it still will need additional bracketry, drilling, welding, etc to get mine back to solid.
I found out yesterday evening that my upper passenger side box is trashed worse than the lower drivers. The 3-link is putting a crazy amount of stress on the lone upper arm.