It will fit all of the motors . But on the 500 a little hammer work is needed.. At the very bottom some dimples must be made for the rod bolts.. Sometime they just touch the bottom and the hammer is needed.. So check the clearance. and one more thing, on the pick up tube , the tap that bolts to the main bearing is a little lower on the bigger motors, not sure about the 425 if its lower or not, but the tap must be bent and a new hole put in closer to the end of the tab..