Blue Jay

I've got a 72 cutlass with power drum brakes. The Brakes started to fade, and then they finally went out. I bled the brakes until I was blue in the face, and have every bit of air out of the lines, but I still have no pedal pressure when the car is on. I thought that it might be a wheel cylinder, but I pulled off all of the drums, and it didn't look like any were leaking. ie none were wet, but they went out about a month ago, so it could have dried since then, but when I get in the car and pump the brakes with the cap on, nothing leaks out anywhere.

When I bled the brakes, I used a mityvac on the back just fine, but when I tried to use it on the front, about 50/50 air/fluid mixture came out, but when I pumped, it was all fluid.

Can anyone tell me how to diagnose which wheel cylinder it is if that is the problem, or if anyone has any other ideas, I am open to them. I am fresh out myself, and getting ready to take it to the mechanic if I can't come up with anything.