Ludwig, You may not have to shorten the driveshaft. If
it will slip together enough to get the coupler
onto the overrun clutch, it'll be fine. I had to
extend my shaft when I switched tractors recently.
If you do need to shorten the shaft, I would take
the existing shaft to an implement dealer and get
them to assist. They'll probably either be able
to do it there or know where to get it done.