1970 Longhorn DriveShaft??

[quikcam]

I bought a 1970 Longhorn which had a gear vendors overdrive unit installed in it. Therefore the rear section of the driveshaft had been modified. I am in the process of putting it back stock. I have the fwd part of the two piece driveshaft but don't know exactly what length rear section I need. Does anyone know what will interchange with the one I need? Are all long bed truck the same rear section and the front section is the part that is different or am I stuck with finding one from another longhorn??

Help.