OK, I talked with Ernie my co-worker and he confirmed what I had thought. Wilwood told him that even though disks take more pressure to operate than drums, they are more effective. They told him that it was unusual (disk rear and drum front), but that others had done it and they sold him a dual circuit master cylinder and proportioning valve where both the front and rear lines from the master go into the valve, but that the front valve circuit was just a pass-thru (basically a junction block) and that the adjustment occurred on the rear brake circuit to keep the rears from locking up. They recommended it be adjusted with a pressure gauge, then a cautious test drive and further adjustments to get the brakes balanced.Oh his setup, once he upgrades the fronts to disks, they told him he could take the valve out of the rear circuit, but should at a minimum readjust it to restore proper braking balance.
Hope that helps. Again he said that Wilwood was very helpful when he talked with them and he had not yet bought anything from them at the time, so you might give them a call to confirm. With some particulars on your vehicle, they could probably give you some good recommendations.
Good Luck
