American Motors: bad brake pressure, proportion valve, adequate pressure

Question
i have a frame off 1976 cj7 complete new brake
system i changed the proportion valve to a disc
drum combo has a new 1992 booster & master
all lines seated good have good pressure at rear
but weak on front. back want's to lock up first
freeplay on pedal seems right slightly apply and
it squirts up in the front bowl pedal feels good and hard until i start and the pedal goes to the
floor i'm stumped
                  stuart

Answer
Sorry for the late reply, I've been out of town on business.
Could the lines at your master cylinder be reversed? Is you proportioning valve causing a problem? Do you have adequate pressure going from the master cylinder to the P valve? What's the pressure like that leaves the P valve and goes to the front, at the P valve? Does the 92 booster/master cylinder work with the 76 system?
Just some things to check.