Rear brake lockup after hydroboost install

[Hertzdaddy]

I don't know if its related or not but my rear drums on my 73 Jimmy are locking up very easily after doing a hydroboost conversion (from vacuum assist.) The hydroboost system was from a 79 diesel and works well for the front discs. Was there any difference in the prop valve for the hydroboost system? Any other possibilities that might cause this? I didn't change anything else with regard to alignment or suspension adjustments.

BTW, I switched the system to hydroboost due to the lack of vacuum from my choice of cam.