http://www.mustangii.org/decoder/axle/
By looking at the differential you can see the shape and it will tell you what specific car it came from. my Monarch II has a Pinto gasket on it . Supposedly the Mustang II and several other Ford products use the same gaskets from that time period. You can get driveshaft knuckles at NAPA along bearings,seals and pinion seals.