I found a good deal on a swingarm bearing kit for a 98 YZ400. It's a pivot works part #PWSAK-Y06-421. I went to pivot works website and they listed the part number for my 99 YZ400 as PWSAK-Y07-421. My question is whether there is a physical difference between the parts or wether they just change the part number every year. Hopefully one of you can tell me.