I'm not convinced I will need it, but in the relative schema of things, $67.99 for a proportioning valve I may need to help the car drive a little better and be a better summer DD is all right by me.

I gotta get all my front end projects done so I can drive the damn car before June - the brake system is the only thing I needed more parts and pieces for.

The stock COMBINATION valve is inappropriate in an all disc setup.

very cool - I didn't even know about this, I bought their inline one.

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Whats the Wilwood part number for the adjuster?
Thanks

What about a combination valve from a 4 wheel disc grand Cherokee or an explorer?

Different animal altogether, different functionality. Assuming similar sized rotors and calipers they could work properly. But all you would gain over the aftermarket one shown above is price, having a functioning brake warning circuit and only by giving up adjustability. Unless you know, and I do not, that it will work right go with the unit shown above for an all wheel disc setup.

Would it be a terribly big deal to go with the stock combination valve for my disc/drum setup?

I am only wondering because the Wilwood valve will require me to buy additional tools: a flaring tool and a line cutter in order to use my existing brand new lines with that valve.

If I really need one, I may just go back to the original plan and use an inline valve on my rear brake line (which will still require me to cut and flare, but not to cut and flare brand new lines).

Stock type disc/drum combination valves are designed to mate the different physical characteristics of the stock disc and drum style brakes.

Discs always have their pads touching the rotor so it's virtually instant on. Drums do not have the shoes touching the drums so there is some delay before application. One of the functions of the stock combination valve is to "HOLDOFF" the pressure to the front brakes until the rear shoes touch the drums. This allows simultaneous application of the brakes at all four corners. Using this function in an all disc setup will apply the rear brakes before the front brakes. Not good.

Stock modern style drum brakes are self energizing, which boils down to this, they do not apply braking force in a linear fashion. The stock combination valve will slow the rate of increase once rear line pressure hits a "HINGE POINT". Using this function in an all disc setup will make the rear disc non-linear in relation to the front brakes. This may or may not be an issue as weight tends to shift forward decreasing traction in the rear, only testing can determine if this is so for your setup.

Those are the two major issues using a disc/drum combination valve in a disc/disc setup. I would not do it, but I am sure there are plenty of people who have and will tell you "it works fine", those people don't understand how the stock system works and cannot comment knowledgeably on it. You now can, because you know and you can now make your choice.

If you mount the manual proportioning valve next to the master cylinder you only have to bend the 'original' line over to the new valve, and add a short line from the prop. valve to the rear line's port on the master cylinder. That's how I did it. I think I have a picture some place.

If you mount the valve next to the driver's seat, then of course you'll have to cut and flair.

I have a picture, but it isn't close enough to show enough detail.