5 The Pro-G suspension system isn't a Saturday afternoon bolt on, but instead an extensive project for those with time and fabrication skills. The Mustang's front framerails are little more than reinforced sheetmetal boxes from the factory, which is why Heidts includes heavy steel plating, which must be welded to existing rails. Once shock towers are removed and surfaces cleaned up, reinforcement plating is welded in place. Heidts wants you to measure carefully and do it at least twice. Once you've welded all this heavy stock, there is no turning back. While you're at it, consider the installation of torque boxes for further chassis stiffening.