side stand is forward of the foot peg on the 500,the 550 later frame with the passenger pegs on loops is behind it,the early 550 frame is the same as a 500,the later 550 swing arm has one grease zerk in the middle of the pivot,the early ones and 500s have one each end of the main bolt,the right hand peg forgings are longer and the rear brake lever bush is in a different position on the later 550,i think the early frames steer better.