Hooker stainless headers are over $500 so I'd say $300 easy..... "no name" does not always mean cheap or shotty. I just bought some Ebay long tubes for my C6 and the quality and fit is just as good as the Hooker sidepipe headers on my C3. The mounting hardware that came with my cheap headers was junk, overall less than half the price ..... then again, the mounting hardware that came with my $1500 Hookers is junk also....
Do you have a car without exhaust so you can verify fitment? The primaries are 1 5/8" and the flange is 3/8" ??