my brakes don't seem to work correctly under any circumstances

What is your question?

I'm having problems with my 1982 Chevy C20 step side 2WD I have replaced the master cylinder, brake booster, and proportioning valve, only to still have my pedal go all the way to the floor before scratching the surface of my brake pressure. as I press the brake pedal I essentially have to go through some fake pressure on the pedal that isn't doing any stopping power in order to get to my actual pressure that stops my truck, I was also having problems before I installed the new proportioning valve where I just barely tapped the brake and it locked my wheels up, I have no idea what's wrong or what could be wrong at this point and am desperate for an answer

What makes this problem better or worse?

when i punch the pedal it hardens for a split second

How long has your 1990 Chevrolet C2500 had this problem?

A few weeks