Master cylinders usually have some level of proportioning in them, but they are typically designed for the rear well to provide fluid to the front brakes, front well to the rear. If your dual master was originally used with disc brakes and you have drums, you'll need to add an inline 10 lb. residual pressure valve, available from Wilwood. Place it in the line right outside the master cylinder. Not knowing what your master came from, you may need a proportioning valve but its not likely.
