Thanks for your response, but yes, I purchased a 1976 Runabout. I checked at RockAuto.com where I get a lot of parts, but I didn't see any proportioning valves there. Do they sell these at the local parts store or do I have to get these from a junkyard? I do have a booster I bought to use as a core since it seems like I will need a core to get a rebuilt unit.