Brake help.....?

Yep master cylinder needs replaced. A quick test is to have a wench that will loosen the line nut at the cylinder. When it locks up on you, you should find that when you loosen the line nuts (one or both) that pressure will escape. If so then the fluid is getting behind the cups and cannot return.

Now about the master cylinder being different, do you intend to put this car as mint manufactured condition? If no then go with the current system, it is safer than a single reservoir. But if you are putting this car back as it came from the factory then you will have to change it to what is called for.

On winning the car shows how is it entered? If Custom Classic then you are fine to use the dual reservoir system. If in the Factory Mint Condition the you need to go back to original. Personally I like safety, I would leave the system that is there and repair it.

Sounds like the ROD where the Master Cylinder mounts is adjusted 2 long - The rod has 2 have a little play so there isn't

constant pressure on the master cylinder plunger..I hope NOBODY put power steering fluid in the reservoir - if so ,U need to rebuild everything rubber..

First make sure you have free play in the brake pedal. If you use your hand on the pedal you should feel1/8th to 1/4th inch free play. With no free play the master cylinder can't release the pressure and it will build up and finally lock the brakes up.

If you have the wrong master cylinder that is another matter.

all car prior to 1968 have single reservoir master cylinder after 68 any new car was required to have duel reservoir so if you lose a brake line in the front or in the rear the other set will still slow the car down.

I would check the calipers. They might be sticking when you apply the brakes. I had a Cadillac and the drivers side front caliper did teh same thing. I hit the brakes the left front would stick causing the car to pull really hard to that side. The master cylinder was working as it suppose to.