Who has experience with a rear disc brake conversion on their Mustang? I'm looking at making the switch to rear disc on my 67 "S" GTA Fastback, but I hate surprises - like buying a "complete" kit and finding out that I need to buy "this" or "that". I currently have power front disc and an adjustable proportioning valve. The master cylinder is for power front disc and drum rear. Kit/manufacturer suggestions please?