Been running original single pot master cylinders on all my cars that came with them for 45+ years. 1930's and 40's cars, my '61 Corvette, '65 and '66 GTO's over the years, etc.
The drum brakes will lock a wheel as well as a disc on a panic stop....just not many times in a row. Disc brakes up front are a legit upgrade, in the rear are a waste and a down-grade, IMO. I drive 4 wheel drums both power and manual and have for decades and hundreds of thousands of miles and I'm still here. But then, I don't talk on the phone or eat while driving.
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Jeff 
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