How will this combination work? I know it is not ideal but the problem is I already have a built 31 spline rear end with c clip eliminators.... This would just make life 1000 times easier. What will I have to do about the proportioning valve and master cylinder?
To my knowledge the factory proportioning valve on a cobra doesn't have the internals and the work of that is left to another prop valve at the front/rear union. So if you wanted to you could get an adjustable prop valve and install it where the brake line feeds the rear brakes so you can manually adjust the proportioning from there. Other wise, if you already have the cobra proportioning valve that goes to the master cylinder, you would need to find the spring and plunger for the inside and get yourself a plug that has one of those little holes in it. I'm not 100% on that but that would be my guess.
Unsure as to which MC to use, but go about the prop valve as if you were installing rear disk brakes.
Use the Ford Racing part ot "gut" the factory internals of the stock prop valve and install an asjustable valve at the brass union on the pass side firewall.
This will allow you to dial in a little more rear brake pressure if, for example, you have wider stickier tires offering more grip.
Honestly it's something i would do on a stock Fox system period. The way the brakes lines are plumbed is retarded. The driver's side front brake sees direct pressure off the MC and the other side is proportioned with the rear. I guess ford's reasoning is if you lock the left side front up, the car will pull to the right...away from oncoming traffic.
But a new MC with a 3-2 conversion and adjustable prop valve is the way to go