[Alan Roehrich]

Stock master cylinders, and some stock systems, often include a residual pressure valve. It is not necessary unless the master cylinder is mounted below the calipers and wheel cylinders. So you do not need one.

A 69 Camaro was available with 4 wheel disc brakes, and the pieces can be found. Not sure what your rules actually specify, since you say "stock/oem type setup". Stock GM stuff does not lend itself well to really self retracting. All calipers drag at least a little, since the pedal would be low and require a lot of travel if the pads really retracted any appreciable amount.

In order to keep drums from dragging, you have to run them loose, usually about 4-6 clicks back from the normal self cleaning and self actuating position you would use for street driving.