I'm in the middle of replacing my booster, master, and prop. valve on a disc/drum set-up. If I use one of the new brass combination valves, do I still need to use the old Proportioning valve on the frame under the driver's seat?
Also, one supplier's website (Master Power Brakes) says to install a 10 lb residual in the outlet for the rears (drums) while others say it's part of the newer valves. Are they not all the same?

Thanks in advance.

If you are going to install a new Power booster, master and Proportioning valve at the Master, then you do not need the one on the driver's side frame rail. You will need to change out your front to rear brake line to eliminate the Prop valve on the frame rail. I believe that the brake system will not function properly with two valves although I have seen people use the dial type of Prop valve used in conjunction with the main prop valve. Maybe others will chime in to confirm this.