have you guys looked into the ice engine works header mock up tools? They are really awesome to play around with getting the header design perfect before hand. I've done headers, and even though I'm not a pro at it...just taking the time to play around with different setups/ideas really comes out as a better product.
Icengineworks complete exhaust fabrication systems allow you to go from concept to completion of custom headers, turbo manifolds, and full exhaust systems.