Which driveshaft?? (Dart/Scamp)

I have a '71 Scamp with a 318 and 904. The rear is an 7.25. The current driveshaft is to short. Does anyone know the length or an application that would work? The rear will be swapped soon to an 8.25.

I am guessing a '74/6 Dart with a 318/904/8.25 would obviously work- but there isn't any of them around here!