need brake help

[vardenafil]

i have a 1972 k20 pickup. The brakes never worked from the get go. The previous owner stated that the brakes just need a new rear cylinder. but if the fix was that simple he would of fixed it before he sold it. when the truck is off the pedal is low but hardish. it doesnt get hard until the bottom of the pedal stroke. soon as i turn the truck on the pedal drops all the way to the floor. there is no stopping power what so ever. when i turn the truck off the pedal pushes back against my foot several inches.

since owning the truck i have done the following brake wise.
- replaced front and rear calipers
- replaced all rubber lines. switched to braided steel lines.
- replaced the master with a disc/disc master.
- replaced the proportioning valve with a disk disk master.
- bled the truck using numerous times using different methods.
- checked to make sure the pedal attachment is in the right hole.

im at a loss at what to check for next. the only thing i havent replaced is the booster. but if the booster was bad the pedal would be hard not soft and spongy right? Any ideas what to try next?