I own a 04 chevy silverado 1500. The brakes are spongy ( I've bleed them throughly, new everything except booster and master). My work trucks brakes are great 06 Sierra 2500 hd dual piston calipers all the way around same pads as the ones in my chevy. The question is can I upgrade to a dual piston the rear? They currently have the wimpy single piston. If an upgrade is possible do I need to upgrade the Master cylinder to accommodate the extra volume? If so can I just order the 2500 hd master cylinder?