Sounds like you might be talking about the overrun coupler?
If you have the original PTO shaft it is 1 1/8. The only OCR I know of for 1 1/8 is the one with the roll pin through the pto shaft. If you want the spring sleeved ocr, you need to convert to a 1 3/8 pto shaft. Also, the newer implements use the 1 3/8
The kit on site that comes as a complete preassembled unit with bearings, screw on cover, and all. It is exceptionally easy to switch out. Unless something is goofed up on your splines, maybe a 15 minute job.