00 Brake Issues, what to do??

[SkylineNXS]

So i was wondering if anyone has or had the same issue as i do. With the truck in park and running, i can pump the brakes a couple times and get to a point where i cant push the pedal down any, but when its in drive i can never do this. In normal driving conditions, i can push all the way down on the brake pedal until it hits the floor. When braking, the pedal has a kind of nothing zone where it does nothing and then the braking starts, id say about half way down. I am assuming this is a master cylinder problem, but has anyone had this problem and fixed it? Only reason is that when u slam on the brakes, the stopping distance is huge, id never be able to avoid an accident with it like this. Thanks...

BRAD