There are other headers out thar :

http://reds-headers.net/index.php?main_page=index&cPath=10&sort=20a&filter_id=1

Some of the Headers shown may have a performance advantage.. but those 1-3/4" & 2 " single main tube ones are probably a waste of money. They likely are little if any better than 57 up manifolds, & not to mention the increased noise & likelyhood of exhaust leaks.

Paul