Brake Line and Prop Valve Plumbing

[wxman1]

Have finished the rotors and caliphers on my 69 C-10 P/U truck upgrade.
Have installed a disc brake M/C and a proportioning valve. Below is a pix of the valve. It shows 2 ports for the front and a large one for the rear. Do I need to run 2 lines to the front(one for left and one for right)? The dealer said some people plug one of the front ports and run the front disc brakes off the one remaining port.

Has anybody actually used this particular this prop valve before? Did you run 2 separate line on the front or just one?

Jim