This is an original used Ford 9" Nodular Iron Third Member 31 Spline 4 Pinion Traction Lock Posi.  Removed from my 1969 Boss Trans-Am Mustang.  Complete with all hardware.  (Does not come with pinion or gears.)  This item that has been used previously.  This case is nice and with no cracks.  This 9" Nodular Third Member will fit other Ford Models as 1965 - 1970 Shelby Mustang GT-350  & GT-500.