tonys91rs

iTrader: (17)

i recently dropped in a 10 bolt rear disc that had been rebuilt with a posi and 4.10 gears. this rear came from an 85 iroc. the brakes are the stock iron calipers. it worked well in the iroc prior to going into my 91 that had rear drums. the drum rear works great in the iroc.
the disc rear is not working as well. the brakes have been bled a few times but the pedal still feels soft. on jackstands the driver rear holds the rotor tight, but the passenger side does not. the ebrake cables were also switched and will not hold on the disc rear. im unable to adjust it above the drive shaft as there is no adjustment shaft and nuts.
is there a problem with the calipers or not enough pressure going to them?
i researched before and after to find a solution and picked up a proportioning valve from jegs to put in. ive read where they have been put in under the master cylinder and under the driver seat area. where is the best place for it? in the same article, the distibution block was modified as the spring and plunger was removed and the screw put back in.
any ideas and pics would be helpful.