The new headers for the 582 I will be getting from The Fab Shop will be 2 1/4 inch tubes. A lot of it will depend on your bends. Can you make a smooth bend using a size tube from flange to collector? If so, you would be able to run a smaller tube. If the bends will be hard, then you are more then likely going to have to step the header. I would suggest you give Tim at Fab Shop a call. Even if you build your own, I am sure he will point you in the right direction. 317-294-4323