If you are self bleeding, you can use a hose that is immersed in brake fluid and fits tightly around the bleeder screw. Start at rt rear and loosen bleeder; SLOWLY pump pedal about five to fifteen times, using about half a cylinder of fluid thru ea wheel. Keep an eye on fluid. Start at rt rear then lft rear, rt front lft frt. Brion Traill
One other thing to check that can sometimes make a difference is the flex hoses. Sometimes they can clog(especially old ones) and this can cause some problems). I did both the front ones on my 66 and my brakes are great. Steve Charlton
We did a 63 300C and the brakes were all new, and the pedal still went to the floor after bleeding. We went back in and manually adjusted the star wheel on each drum and found them to be 3-4 turns out. After that, the brake pedal was rock hard and stopped us as well as drums could in a 4000 lb car. Should only have about 1" before you feel resistance. Make sure when you adjust the star wheels, you pump the brake to reseat the shoes. We had to do this twice on the old 300. Steve Wander
A loose star wheel adjustment would explain your symptoms perfectly... when rolling, the shoes are actually supposed to touch the drums slightly, not enough to drag the vehicle but enough that you can just barely hear them scrape when you spin the wheel in mid-air. If they don't touch the drums, then the first thing the hydraulic fluid has to accomplish is moving them into position, which takes a fair percentage of pedal travel. A properly adjusted brake system gives the feeling of stepping on a rock. I've found it to be tremendously more satisfying than any power brake feel.
The comment about reseating the shoes... yes, I've always found that if I adjust the star wheel while rotating the drum until the drag feels just a little too tight, then go step on the brake pedal once to "seat" the shoes, I come back to the drum and discover it rotates slightly more freely. Must be something to do with the geometry of the mechanism. I like doing it this way because I know that the final adjustment will be accurate under normal driving conditions... and because it's easier to get left and right to feel the same, so the car won't pull in either direction. Erik Ievins