There are a lot things that could cause your problem. Check the easy stuff first.
If you want to make sure you have all the air out of the system and that you don't have any bad hydraulic components, run the adjusters out so that all four wheels are locked up. Now see what happens when you step on the pedal. You should have a slight amount of free movement at the top of the pedal, but as soon as the rod contacts the piston in the master cylinder it should stop. If you keep holding pressure on it, the pedal shouldn't go down. If this is what you get, the problem was that you had the shoes backed too far off the drum.
When the rod hits the master cylinder pedal, if the pedal starts out feeling "mushy" but you can pump it up tight and it will hold pressure, you have air in the system.
If it hits and feels hard, but continues to travel down slowly when you hold it under pressure, you've got a bad hydraulic component . . . if you can't find any leaks, it's most likey your master cylinder.
Another problem to look for is no free play between the rod and the piston in the master cylinder. Before you go adjusting anything there, make sure that you clean all dirt, rocks, pennys, carpet fragments, etc. from around the pedal stop. After 30+ years, there's no telling what's packed down in there. This junk will keep the pedal from coming all the way back up.
One last note . . . if you want ALL of the air out (and believe me, you do), pressure bleed it. Look back a page or two in this thread for instructions. Oh yeah, I haven't found a complete set of belts, but I'm still looking.