42 brake master cylinder on a 37

[pete rose]

Hi Guys
I'm on my second master cyliner due to the first one leaking
at both ends. The second one has no leaks but has an issue that I need help with. when I drive the car I need to use the brakes to stop the car on a hill
by my neighborhood at a light. then there is another light a short distance away
followed by another stop sign.After pumping the breaks to make these stops the brake pedal gets harder and harder till the brakes are almost locked on..
Anyone had this problem and know a cure? do I need a better Master cylinder?
It seems like the internal residual valve is working incorrectly..
Need suggestions for a made in America master cylinder or any other suggestions the Barn experts can offer me
Thank you, all help appreciated as usual
Pete