You do need both. The distribution block splits the fluid flow from the master cylinder to the four corners of your car. The adjustable proportioning valve will go just behind the distribution block so as to be between the distribution block and the rear brakes. The kits I have done included a brake line about 6" long that threaded into the back of the distribution block. the adjustable proportioning valve went on the back side of that 6" brake line. Then you have to cut and flare the brake line going to the back to make up for the extra pieces you just installed.
