No joke: cut the shaft with an ordinary hack saw (new blade). Stainless steel cuts like butter at slow tool speeds. Treat yourself to a new file if necessary to round the cut end off.
A drill press is really nice to drill the set screw recesses. If you have to drill them free hand, go real slow with the bit. Either way don't forget to use some light weight cutting oil. Hole is 5/16". I only drilled mine on the flat sides. Shaft is captive if you put the vibration reducing joint next to the rack, so the set screws only need to lock everything together.
As stated, you can push a DD shaft through the non-vibration reducing U joint during installation to make it shorter, then pull it back down and lock it after the assembly is in place (one advantage of DD over splined shafts -- splined shafts can't push through the joint).
Was Gil your Borgeson rep? He should be getting quite familiar with DeLorean sales by now.