The main purpose of the dual master cyl if you blow a brake line or hose you will still have some braking power left as with the single cyl you lose it all. I think if you rebuild your present system, replace all metal and rubber lines, and the hydrovac is working properly. You will be suprised at how well the truck will stop. One thing you might want to try ( if you can find them) is the new brake shoes with the kevlar lining. I hear they make a big improvement.....Mike
