I agree that the primaries seam to small, if you are looking for all out performance.
There are many cobra builders out there that are buliding cars that are not about all out performance. So these headers would work.
I am on my soap box now,
All claims aside, to buy a set of mandrel bendt Headers to fit an LSI in a Classic revival for $800.00 is fantastic, the fact that they are available is amazing. I hope this is a trend that continues, so that parts like this become available, it will take a lot of stress out of building your kit.
If you want real power though, you need to get A FORD.
Phil