Power brakes don't improve your stopping power, they just make it easier on your foot. Pedal effort is the only thing that is different, the actual brakes are the same, so is the stopping distance. Honestly, I prefer manual brakes. My challenger has power brakes, but my duster has manual brakes and the manual brakes have a much better pedal feel. Both cars have 11.75" disks. The duster had to stay manual because of the cam in its 340, but I'm glad I kept them. Heck I may even convert my challenger.