Wtb--mt driveshaft

I have a 727 driveshaft that came with the car and it is approx. 4 in. shorter than needed for the manual A-833 trans.. My interchange software shows the length, (weld to weld or center of u-joint to center of u-joint, I don't know which?), of the auto trans driveshaft as 48 in. with a tube diameter of 3 1/4 inches. the manual trans driveshaft shows as 51 31/32 in. with a tube diameter of 3 inches. Shows to be a 70-71 Dart or Scamp only for the auto, or 70-71 Dart manual whichever length with a 29 spline yoke and a removable carrier. Ben.