Any good reason to use an adjustable proportioning valve on my 70 Mach with front disc and rear drums? Should I stay with the stock distribution block until down the road when I will upgrade to rear disc. How does the adjustable work anyway? It has one entering port and one exiting port. Would I need two valves to run the front and rear? Anyone have pics of their setup? Where is the best place to mount the adjustable valves in the engine bay?