brakes sticking...thoughts?

[sactoC10]

Picked up this GREAT 1971 1/2 ton 350 long bed from the son of its original owner three weeks ago. The truck was well maintained and taken care of by dad, but basically it has sat for the last few years.

Put dropped spindles on it over the weekend and while in there decided I might as well put in new brake pads. I found it odd that as one set went in, the fluid level in the reservoir did rise. Instead, the cylinder for the opposite side got pushed way out. It was then impossible to push the cylinder back in, even with a C-clamp. I ended up having to remove fluid from the bleeder in order to back the cylinder in to install the new pads.

Now since I've had the truck the brake light has remained ON. replacing the pads, adding fluid, etc... seemed to get the light back OFF. Yet, my test drive last night was not good. Brakes still stuck, had to mash the gas to get it moving, which happened once before.

Any ideas? Master cylinder shot? Something else? HELP!!! I gotta drive my truck!