There were 2 models of the 2001 SnoPro 440. A Cross Country Version and a Sno Cross Version. The SnoCross one had a hotter ignition timing at low and mid range than the Cross Country version. You might want to get the "500" program put into it from the factory. There were only one set of heads and cylinders for that model. Make sure that the sled had the Cylinder Update that was done for the consumer sold sleds and you should be good to go. Make sure you have big enough jets for the temp and alt.