I have owned, tuned, and rebuilt all of them. Any one of the Speeds is a good choice. My favorite is the MAG version, but the Al and Worlds are just as good. O.S. drilled the AL head on the Worlds Ed to reduce the weight without using the MAG head to keep the cost down. I never have had any heat issues with the MAG version either. Use the OS 2060 or Ninja 2042 pipe with the OS round or square header and a 7mm carb restrictor.