You came to the wrong place for that because you're dealing with a lot of custom fabrication. What I CAN share is the manufacturer spent a real lot of time and research on designing a carefully balanced brake system, front to rear, and there are no standard parts that are going to meet your needs without a lot of experimentation.
Drum brakes are self energizing so little effort is needed for them to lock up the wheels. You can't do much better than that as far as stopping power. The combination valve contains a carefully calibrated proportioning valve to prevent rear wheel lockup under hard braking. That will be totally different with rear disc brakes and with different weight distribution. Trucks are relatively light in the rear compared to cars so even if you just leave the car chassis alone and put a truck body on it, you'll have easy wheel lockup on light braking.
Everyone who has built custom cars has gone through the trial and error process of making systems work. You're in for a lot of fabrication and modifying. We don't get involved with that here partly because of the potential for lawsuits and partly because that is not our areas of expertise.
Saturday, April 28th, 2012 AT 6:21 AM