On your original question, is a cast iron 3 hp wheel safe for 8000 to 8500 ? I'd have to say yes, we ran them on opens for years, turning them higher than that. You would want to use one that hasn't been beat up, or machined in any way. When Limited's started turning rpm's in the 9000 + range the stock 5hp wheel showed it's weakness a few times and that was more than enough to mandate a billet wheel, the 3 hp wheel with it's smaller diameter and lighter weight doesn't have quite as much force acting upon it trying to tear it apart. I've never heard of a 3 hp wheel coming apart , and it was the wheel of choice for opens for a long time. Anyone out there have a bad experience with one ?