There are motor mount brackets available to bolt the 580 in that chassis. I have a set I could sell you, $50 shipped. I have done several of those switches. You have to do a little modifying of the airbox and a few other things but overall it is pretty easy. In my opinion the 580 was a better engine anyway. You need to replace pistons in the 580 about every 2500 miles though, the pins that keep the rings from turning have a habit of falling out after so much time. Keep your drive clutch in good shape and a 580 will last a long time.