Front brakes do 70% to 90% of the stopping due to weight transfer toward the front during a stop, so it makes sense to upgrade to a more efficient front brake. Unless you're in the habit of hauling maximum loads in the truck bed, the rear brakes are mostly for stability. Even if you choose a disc rear brake setup, the pads and discs need to be smaller/less efficient than the front to avoid rear wheel lockup. Some trucks use big rear brakes capable of stopping max-weight loads, and use a proportioning valve to reduce rear brake efficiency when the springs are unloaded.
Jerry
