You won't be needing a proportioning valve. Here's an excellent thread I stumbled upon many years back that contains a wealth of information related to a dual reservoir master cylinder upgrade. Good luck to ya and be sure to share how your conversion works out
http://67-72chevytrucks.com/vboard/showthread.php?t=460791I also have a printed copy of a thread from here on the Stovebolt from May 2009 entitled "brake...master cylinder" where dave64 states the following:
"I just changed my 66 over to a manual (no power) 4 wheel drum dual master cylinder a few weeks ago. Running the lines was the toughest part.
Go to Partsource and ask for a master cylinder from a 68 1/2 ton chevy (Impala etc. is the same one) It bolts right up exactly the way your old one did. I just had to grind the shoulders of the bolts slightly. Uses the same rod from the pedal - you don;t even have to adjust it."
