Prop valve question

[Harold Shepard]

I am currently changing over a 69 mdel truck to disk brakes. I had already bought new brake lines (great deal- $20 for the 6 metal lines in front) with the plans to use the praise dyno brake kit. A 71 parts truck landed in my lap and now I have switchd gears and am using the spindles etc for disks (too far gone to stop- new upper and lower ball joints, tie rods etc.) But now I have a problem and I'm sure some one has run into it. How are you modifing the prop valve from the 71-72 to work with the 69 brake line set-up? By the way this is a power brake truck. Any input is greatly appreciated.