I'd choose to use a larger diameter shaft, maybe 1" or larger, and turn the ends down in a lathe to fit the hardware. Another option would be to weld correct-diameter stub shafts into a piece of heavy-wall tubing like Schedule 80 steel pipe. You're going to need a machine shop to mill the key slots anyway, so the added machining time to turn a larger shaft down won't add a great deal to the cost. Small-diameter PTO shafts have a habit of twisting, getting the U joints out of phase, and setting up destructive vibrations and stresses on the couplings.
Jerry
