If the shaft is solid, you may have it milled with some flats. If is hollow, you will have to weld and/or pin the joint to the shaft. On two projects I'm doing at work, I welded the smooth 3/4" end of the joint to the shafts. One was hollow, 49 Ford F1 keeping the old column and adapting to the new chassis which is an 04 Ford Explorer with a rack, the solid shaft is on a 62 Nova being converted to p/s with the Borgeson box and shortened outer column tube/inner tube which contains the upper shaft bearing. Borgeson does make a shaft for the Nova, just for that conversion, but I was instructed to modify the existing one and make it happen.