I had a 10'HCR last year. Pulled the DD off to put the 5203 bearing on, and it fit just fine. Still had some play in the gearset in the case and the 2 case halves fit together without any resistance. I now have an 11'HCR!! Wanted to update bearing to 5203 style, so I removed old 6203 bearing and spacer, pressed 5203 bearing on and the two case halves would not fit together correctly. I ended up maching the shaft down .050 where the bearing race rests so I could press the bearing further on the shaft. This enabled the two case halves to fit properly. Installed everything back to normal and all is good!! hope this helps!! And your answer to "Cat" suggesting the 5203 bearing for replacement or having information on the machining process is, well, NO!! They have no info for this process!!