I assume that you have an adjustable aftermarket Valve and are not looking for originality, just a professional installation. If so.
The valve should be installed in the line going to the rear brakes. There should be nothing between the valve and the rear brakes that would change the line pressure to the brakes. Typically the valve can be mounted below the master cylinder. The line from the master cylinder will go to the valve then out of the valve to the distribution block on the frame rail. They recommend that the valve be secured to some thing sturdy rather than just letting it hang on the brake line. A good way to do this is to fabricate a small bracket and bolt it under the master cylinder by using the master cylinder to diaphragm studs.
I have mine installed this way and it seems to work great. You will have to spend some time adjusting the valve. I adjusted mine by doing several hard stops on a dry hard surface. I started with full line pressure to the rear brakes and the rears locked up early. I backed off on the adjustment with the goal being to have the rears lock up just prior to the fronts. As I backed off the adjustment it became more and more difficult to lock up the rear brakes until finally I can almost not lock them up at all. A full on panic stop in my car will not lock up the fronts and rears just start to "skip" a little. (and my face is plastered to the windscreen)
Hope this helps.
Clark