Brakes sticking... I need your help

[AJohn6]

I installed the CPP power brake and rear disc conversion kit on my '71. i am having a problem with my master cylinder, I think. While driving the truck I can reach down and pull the brake pedal back about 1/4-3/8 of an inch. It doesn't do it all the time and I have tried adjusting the little post that comes out of the booster. I got more play out of the pedal but it still does it. I have new brake calipers and associated parts installed as well. I can tell its causing the brakes to have slight pressure on them because when I forgot to pull the pedal out I stopped and felt all of my rims and they were hot as heck. When I don't forget they feel fine. I am at a loss, and I need some trusty advice from you guys.

Thanks in advance,
Adam