I've never had a bad booster cause the pedal to go to the floor.
You can check the booster easily by applying the brakes in the morning, before you start the engine. Pump them up if you have to. Then, while holding your foot on the brake pedal start the engine. The pedal should move towards the floor some. If it does, the booster is ok.
My bet is on the MC.

 

Amsandunn,

After I pump up the brakes and hold it down, it does slowly keep moving, not quite to the floor but I do sense that it's heading there eventually. To me, it sounds like the seals on the master cylinder are worn out (probably due to my negligence by not replacing the brake fluid on this 15 year old truck). I'm going to check the vacuum line first before I order an oem master.

Thank you.

 

I am with everyone else, it screams bad master cylinder.

 

Thank you everyone for your input. I really appreciate it. New master cylinder comes next week and I'll post how it turns out.