Brake line size

should have a residual valve in the back with drum brakes, and the adjustable proportional valve in the front.
3/16 should be fine.

The front tires will lock before the back because the amount of rubber contact on the track. It takes more brake force to lock the rear tires up because of this, the only time the front adjustable valve is used is on hard stops, this just restricts flow to the front calipers on a hard brake condition.

The residual valve in the rear line helps the rear brakes apply the same time as the front so you have even braking.

Before I installed brakes on my firebird, I called and talked to different manufactures. Strange and Mark Williams directed me to using the components above in the same manner.

Willwood, Aerospace told me to use the valve in the back and no residual valve. They were wrong

I can hold my car to 4000 on the starting line and kill almost 10 mph at the cones without tire smoke in complete control. I'm using Strange lightweight front brakes and rear 9" drums. The car runs 10.60's at 123. weighs 3550.