Shiner, was the car originally equipped with front discs? If so, you porbably need to ditch the propo valve. The valve in my 82 malibu is set up to apply pressure to the rear drums before pressure is applied to the front discs. They do this because of the greater amount of fluid required to fill the back slave cylinders and apply the shoes. The discs take far less volume to apply pressure to the discs. Either way, check with the kit supplier. They should have the straight scoop.
Let us know what you come up with.