Rag joint, steering coupler won't go on

[K10-Kansas]

Same spline count, measures to be the same size, but won't go on in place of the old rag joint. I'm putting the new one on exactly how the old one came off and it won't go on lined up in the exact same flat spot position. Not even with a hammer. I haven't tried hitting it too hard. The only thing I can think of is that the old rag joint and the steering box shaft have been worn and damaged in the exact same pattern together so now something new won't fit on because it doesn't match that deformed pattern.

Help. I don't want to replace my steering box too. Any advice?