72 Blazer break question

[N2Clsx]

Looking for some help here with a problem that I can not figure out. The Blazer does have power brakes. A short time before we parked it for a couple of years a new master cylinder was replaced and from then the brakes were never perfect. We have bleeded (sp?) the brakes atleast 20 times now and not really much better. We replaced the front pads and the rear shoes(that were worn) and nothing. I can pump the brakes once or twice and the work like they should. I can get the rear break to lock up but not the front. What am I missing here?
My next question on a different thread was gonna be the vacuum secondaries will not open on the quadrajet. I have a gauge to check it just got to do it. I could have the line plugged in wrong. Around town it runs great. Could the two be tied together?

Sorry for jumping around on the subjects. These are the last two mechanical problems left on the Blazer. I told Jake that after we fix these I will take him to Azusa canyon or somewhere that he can actually lock in the front hubs and play. Thanks for the help everyone.