I just wanted to pass on this information that I read. I thought it was a pretty good article for anybody that was wanting to build some headers or exhaust system for their hot rod. I found this info in the 2008 Burns Stainless catalog. burnsstainless.com. Hope it helps.
A few more links to some good information for ya. http://www.headersbyed.com/ http://www.headerdesign.com/extras/design.asp