Far as I know, they are the same. As far as fitting, you can put the SOHC750 forks complete on a 500/550 too. There might be some difference with the 750 but, I don't see how the 550 onto the 500 would make a difference. Need some more experienced input here! If I'm right, basically , the 550 is an improved and slightly enlarged (engine displacement wise) and improved in the clutch area too. Don't know if that helps. Later on, Bill