When I talked to a wilwood guy at the power tour a couple years ago, he told me that if I ever went to 4 wheel discs I'd just have to pull out the proportioning valve. This was assuming I used their master cylinder.
That's almost bad advice. Really, if you're going to upgrade to four wheel disc brakes, wouldn't you want to optimize them? Yes, remove the prop valve and metering block or combination valve. Replace them with an adjustable proportioning valve in the rear line. Tune your brakes to work best for you and your car.
