I met up with a few of my friends that wrench for a living last night. We all have PSD F350's or Excursions. I brought this subject up in conversation. Late 02 was when the D60 came out in all of them. The SD D50 is not the same as the TTB D50 of the OBS trucks. The SD D50 is an exclusive axle for all SD trucks and Excursions. For all practical purposes its a D60 with D50 steering knuckles and stub shafts. The SD D50 uses D60 center section, Gears, U-joint, and axles up to the stub shafts. I'll bet this is why Ford stopped making the D50 due to it was so similar to the D60, and why make another axle when the D60 will work with no modifications.