In my case there wasn't enough room once the bolts holding the stub axle on were tightened. Hence the need to cut some metal away.
If the driveshaft isn't sticking out far enough to get the spring clip on, there's usually a hole in the end of them with a screw thread, so you can put a bolt in and pull it out. Usually I find that just hooking something into the threads and giving it a tug does it.