Dual piston MC is safer for disks or drums. I posted PN's many times (search). I'll add to Pishta's post that you can use your existing distribution block by installing a 1/4 M to 3/16 F inv flare adapter in the top port, then fit a 3/16" tube. Insure you use a brass 3/16 inv flare plug (not some pipe plug). In my cars, I installed an adj proportioning valve in the rear tubing, in case I ever change to front disks.
Don't believe the absurd claims that front drums can't stop the car quickly. These people don't understand Physics and probably base their impressions on poorly maintained drum brakes. Tires stop the car. If you can bring the tires to the max braking point, which occurs just before the tires skid, that is the fastest you can stop. If your drums can skid the front tires, then they can realize max braking. It is hard to know where that is, which is why most cars today have ABS. It is also important that your L & R brakes are balanced. Many people assemble drum shoes wrong. If 2 of the 4 shoes have shorter linings, they go on the fwd sides. My 64 Valiant had newly rebuilt drums and some gomer put 2 short shoes on one side and 2 longs on the other. That will surely give unequal braking. Drums are more sensitive to variations in friction, such as leaking brake fluid on the shoes. That is due to the self-amplification effect, which is why they don't need a booster. Also, ideally the front will skid just before the rears, and why an adj prop valve is good. Drum brakes do take longer to cool, so if braking continuously in twisty road racing, or stupidly "riding the brakes" down a mountain, the friction material will melt sooner and give "fade". Because too many drivers didn't understand how to use engine braking, the fed's mandated front disks in the 1970's. I think they still need mandatory training before allowing FL drivers on the Blue Ridge Pkwy. Semi-trucks still have drum brakes, but even disks wouldn't let them brake all the way down a steep mountain, so if they don't use engine braking they will soon be aiming for the "runaway truck ramp" (ex. I-80 in Sierras, I-24 W of Chattanooga).
