You can use the existing larger speedo drives, just take a grinder and pretty much remove the entire outer lip. Mine had a tendency to work itself loose after a while and slip on the rotor, a little dab of JB weld and the speedo never gave me any trouble after that. I had to also use a different variety of spacers to get the front disc to line up correctly, it is a giant pain in the rear to get that second disc to seat just right, too much and it will lock up, too little and it wont brake at all. Good luck, and make sure you have plenty of brake fluid for bleading, would have been a lot easier if I had someone around to help.