How many times do you bang your head against a wall before they call you crazy? By 2021 I was on my 3rd master cylinder. First was the original German model, I swapped that in 2016, then again in 2021.  My problem was that its a single circuit system, when the brakes fail the FAIL.  Here is an article on Jbugs that really helped me understand the difference:

Single Vs Dual Circuit Master Cylinder

Fast forward to spring 2023, I tried to bleed the brakes to move the car, it would not bleed. I had my wife, my son,  my buddy Paul, all working the brake pedal for me. Nothing. Again, total failure. I figured if I was going to fix it, the only real way was to replace it all, but I did that already in 2016 and again in 2021, so what was the point?

Finally I understood what I was doing wrong, I realized another big mistake I had been making for a long time, thinking INSIDE the box. This car has a VW 1965 engine and transaxle. That's about the only thing that would be considered a 1965 VW... Some parts are from 66, some from 68 to 71. I think the frame itself is actually from a VW bus. I suspect this because when I attempted to replace the 1965 speedometer cable I was about 2+ feet short.

The car was manufactured in 1978 from MANY different VW parts, I didn't have to stick with the same master cylinder, it was time to change things up.

I ordered all new brake cylinders, soft lines, hard lines, line benders, cutters, everything I would need. I decided to put in a dual circuit master cylinder and try again. This was not an easy task. I could not just slap the parts in, getting to some of them required removing bolts and parts that had not been touched in over 50 years. I had to remove the drums, not an easy task when the wheel bearings are part of that equation.  This is the reason I didnt go full disc brakes, I wanted to try to keep it as original as possible. 

I had to buy a breaker bar and a 32MM socket. The socket was not easy but I found it. Took the old cylinders out, put the new ones in, installed the new brake lines and connected them to the new master cylinder. I ordered a larger reservoir and bled the system Boom I had brakes and I now know if the master cylinder does fail, it will most likely only fail on one circuit allowing me to stop and ultimately replace the master cylinder. I took care when I re-did the gas tank to make it easily removable to make the master cylinder accessible.  It drives and more importantly stops very well now!