I have watched several driveshafts being shortened and built from scratch. Not just a cut and weld job. Most tubes require straightening and is done while still attached to the lathe used to cut the tubes. This is specialised, expensive equipment and if it wasn't needed they wouldn't have it. If you have 2 shafts at least if yours doesn't work out you can have the other one done professionally. My shop motto " Do what you do, don't do what you don't do" All people specialise in something but not everything.
