I'm not a pool pump motor expert, but I did spend LOTS of years industrial in plant maintenance. I suspect the different part numbers are from different manufacturers. They may also be designating different seal configurations or different lubrication methods. That being said, the dimensions all matching is the BIG thing. Some of those numbers might last significantly longer (or go out significantly sooner) than the others, but if the dimensions match, the bearing will work. Pick a brand that has GOOD customer service and a STRONG U.S. presence in the marketplace, AVOID off brand Chinese knockoffs.