DIY Exhaust Questions

I'm looking to begin gathering parts to fab an exhaust for my cb550/4 and am wondering if anyone has done their own before and could offer me some suggestions.

My biggest concern is the mating of the exhaust port to the header. I've been looking at the yoshimura repro pipe at http://www.lossaengineering.com/shop/honda-cb550-cb750-yoshimira-replica-exhaust/ and the mating surface definately has a profile to it. Is there somewhere that sells flanges like those that i could mate my mandrel bends to?

Do you have the original pipes that you can cut the flanges from?

I might have an old set somewhere in a parts bin, but i really doubt it. I've got one daily rider 550 and 3 parts bikes in various stages of completeness. If i had a set laying around it would be easy to see how the headers connect and what the ends of the pipe look like, but i don't have anything easily available. Even if i had a photo or drawing of the headers it would be a great help.

http://www.monstercraftsman.com/xs-650-do-it-yourself-pipe-kit-1-5/ this kit comes with the flanges for an xs650. Anyone seen anything like this for a 550?