new information:
looking at the GM parts website for the ls2 crate motor it states that the motor is used in both the 2006 GTO and corvette. looking at the online auto parts store it shows no gasket for the GTO but shows a manifold to cat gasket for the vette. Felpro 61012.

so the question now is are the manifolds and flanges different between the GTO and the vette?

Cheers,

Rufus