brake lines? master cyl? or both?

I have a 72 Dart with drum brakes. Had to stomp on them hard yesterday stopping the car and then pedal went to the floor. It felt like a line burst. Also, I've been adding fluid to my master cylinder's front reservoir for a couple months every other week or so. This morning the reservoir would not hold any fluid. I'm thinking of getting a set of lines from Inlinetubes. How do I tell if the Master is spent as well. Thanks