Need Help w/ Brakes

[rico7769]

Hello Everyone,
My bro and I have recently acquired our first 67 GMC. Its great to see the website support and all the info we have read from the loyal supporters!
Our dilemma is this, we recently replaced the master cylinder, both front wheel cylinders, cleaned and adjusted all parts and shoes, and replaced the flex rubber lines leading from the steel brake lines into the wheel cylinder. The brakes were bled several times on right and left front. The setup is dual reservior so we did not bother with bleeding the rear as the back reservior did not move when the bleeding was taking place. The setup is drums all the way around (manual, not power assited anything) w/ parking brake lever under the column. We have inconsistency in the pedal. After a few pumps, it seems to be hard as a rock with no travel. Once the truck is put in reverse, it rides down about an addt'l inch or so requiring me to press it again and it returns to high and hard. Brakes still seem very intermittent. I don't think pressure from the master is the issue, however I don't know! We have a steep driveway so I am leery of backing out too much. I read that the brakes have to "self adjust" by driving in reverse at about 10mph and engaging the brakes. I also read that the emergency brake may have to be engaged for the self adjusters to activate.

I can't figure out why the pedal is inconsistent and the truck is not willing to react no matter how quickly or gently I press the pedal.

Any help??