If you have replaced the master cylinder, bleed itt, have a person in the vehicle pump the pedal slowly a few times, and hold it firmly. while there holding the pedal crack the line loose at the master cylinder. do this a few times, or untill no air comes out anymore.
NEXT
remove all the drums, either both of them, or all 4. Make sure theres no leaking wheel clyinders. Then adjust them till they lightly scratch while spinning. Just barely!!!!
Then, remove all the brake bleeder screws and clean them with a paper clip and some brake cleaner. Watch your eyes.
re-install all the bleaders, But leave the rears loose. Fill the resivour, and let it drain down low 3 or 4 times. do not touch the pedal while doing this. Then close them, and open the fronts and do the same procedure. close fronts now.
Now, go push pedal slowly to the floor 8-10 times. if still not hard enough for you, i think you can adjust the master cylinder rod in the vehicle at the pedal.
this should get you verry good brakes, if not, you will either need help from another person, or go buy a mighty-vac. but try this way first.