Duddygoober,
The adaptor you see will bolt up to the orig location on your 51 for your dual-m.c. however what they don't make clear is the rod provided in the kit won't fit up cleanly to the orig location and the bolt they provide is not long enough. What is needed is an off set rod or a longer bolt drilled out so it can be safety wired. Strongly recommend you use a 69 Mustang Master Cyl that has the residual valves already installed. The ones you buy are expensive and more plumbing required to make fit in a tight location. You will need a mustang master for drum brakes. If you have already bought your general motors m.c. you will need a 10 lb residual for the front and back plumbed as close to the m.c. as possible for drum barkes front and rear. If you have disks up front you will need a 2 lb residual valve. Not a straight forward install. You also could try to install the adaptor behind the current mounting location. That would allow you more room, and a straight shot to the brake pedal atch location with a longer rod.
