Towncar MC adapter fitting

I am putting a 85 Lincoln Town car master cylinder on my 85 mustang since Ive upgraded my calipers and rotors. I need an adapter fitting for the rear port on the master cylinder. Ive tried my local auto parts stores and hardware stores and nothing works. Anyone have a part number or an exact size to look for? I saw one at maximum motorsports but its $15 and will take a few days to get here. thanks