You can certainly cut off the yokes if you want, but they are only about $30 for new ones and the old drive shaft will likely sell to recoup a fair part of that or use as a spare. <shrug> It's up to you and what you want to do. I also went 1410 at the same time.
[Edit] I wouldn't fool with a machine shop on this. I've removed the old yokes several times by grinding down the bead and cutting just slightly offset to the tube side with a hacksaw (or more recently, my band saw). Once you cut through the outer tube, the yoke has an inner cast cone that just knocks out. Once clear, grind a nice bevel and reattach as desired. For square you'll have to make sure the base circle for the yokes is big enough or your going to have to get creative. Buying new is cheap and avoids all that work, plus you can get the diameter of yoke you want... IIRC, mine were all “3” Tube yokes and that worked fairly well with the notching for a mechanical fit on the square tube.
