You've described the exact scenario my brake pedal had. It was the result of two problems.
1) You need to make adjustments to the brake system so the pedal doesn't go all the way to the floor. I overhauled mine as my first project as that's the most important part of driving. Master cylinder rebuild, new wheel cylinders and bleeding the whole system.
2) My floor pan was rusted out entirely at the front passenger cab mount. This caused the cab to tilt to the right and the pedal linkage to rub on the left of the hole.
Resolving those two things took care of my problem. Hope it helps with yours!
