Upgrading BRAKES >_<

Do yourself a favor and call Cass; aka, Dr Diff. He will guide you in your quest to stop on a dime.

If you don't change the weight of your vehicle dramatically. ie like an unloaded or loaded pick-up truck. Don't use an adjustable proportioning valve. It's a bandaid for a poorly balanced system. Instead, use the correct size master cylinder and properly sized front and rear brakes to modulate the bias.