Did you look at the gear? Only the early H motors used a bolt on gear. The rest use a press on gear. The cams are the same except where the nose of the cam meets the front bearing. Some are fileted, some are squared off, and some are undercut. Make sure that the gear or hub you use has the clearance on the cam to allow the proper end play of the cam on the thrust plate. Also make sure that the angle of the gear teeth is correct. G cam gears are angled opposite of the H gears. All of the G cam gears are bolt on and can also be made of aluminum or fiber.