65 Valiant small block with Heddman fenderwell headers. Need suggestions on master cylinder upgrade

My 69 Barracuda lost brakes once in about 1977. Pedal dropped as I was slowing for a stop sign. I did not Know about the Dual-brakes design and panicked. I threw it in reverse and gassed it. Then I took a deep breath and thought about it. Then I remembered about the parking brake. I nursed it home vwewy vwewy cawfuwey.
My pedal never hit the floor cuz I did not know to step harder. I learned that on another occasion!
I had built that trans, and it was fine, it was used to me doing stupid stuff; and yes, it did have a 2800 TC in it. I put 2800s in almost every one of my automatic Mopars, save for the three wagons I've had. I luv my Trac-Action Dirt-Jerkers.. I bought several of them on the employee pricing program, back in the 70s when I was working for a company that built them. Still got one.