I have a good friend who runs 049 oval ports on his 454..they're the same casting as the 781's. He did a minor bowl blend, intake gasket match, and smoothed out the exhaust port. He then took them to Creative Flow Management for testing. They flowed 308 cfm at .600 intake, and 215 cfm at .700 on exhaust. This was his first time at porting, if you're thinking of doing it yourself. Mike from Creative Flow Management told him they would easily support 600 HP. It's easy to get good numbers out of stock castings. Well, porting is never easy! But you get my drift. John