I recently got an adjustable prop valve for $28 from Jegs via ebay. I mounted mine high since don't have the warning switch setup you have in 1970. Don't believe the strange stories about DOT 5 problems. It is less likely to degrade any components in your brake system, including rubber seals. Indeed, some British race cars in the 1950's required silicone brake fluid since glycols attacked their seals. The U.S. military uses it. Just don't use it in an ABS car. Not sure that really matters, but manufacturers say not to. Note that DOT 5.1 is not silicone. It is regular glycol and will rust and remove paint similar to DOT 3 or 4. It is the first glycol to meet the higher DOT 5 standards. They are required to call it 5.1 to not confuse with silicone, though that certainly confuses people.