steel steering columns CAN be "replaced" that is: new length of same diameter spliced to a stub of the original (that stays brazed to the crown). It allows a 'too short' to become longer (just right) and a threaded to become an unthreaded.
As John pointed out, along with the total length being important, the threading must be long enough, too, so that the HS will work, whether spacers are used or not, the threaded upper cup has to screw down far enough to make contact: you can't compensate THAT with spacers.