I am not sure if you want a stock appearing truck or if you are into modification. That being said, in my situation, I wanted a stock appearing truck. There are replacement wheel cylinders available for not too much money. NOS master cylinders are there as well. AB Linn has shoe lining for sale on the auction site right now. Front and rear brake hoses are out there and not that expensive. And the steel line is conventional 3/16" or 1/4" depending on location. I know that many advocate changing to dual master cylinder, disc brakes etc. I am not against any of that. But from my perspective, I enjoy bringing it back to original. It worked in the late 60s and with good parts, it will work today. Those huge 13" drums have a lot of stopping power.
I realize I am not an engineer. I have left it to the Kaiser Jeep engineers to design the system, which I feel worked, so that is what I went with. As they say, "It just works". And I don't have to figure anything out.
So, one person's two cents worth.