Just to be clear, the Dutra Duals are split manifolds, they are not headers. They're good though and I like the quality. I've seen a pair of the Aussie Dutra Duals up close and personal rather recently. They're nice. Be careful though. Do your research, because those don't always fit with every intake manifold out there for the slant 6. Maybe you can start a thread and see if anyone runs that combination and how the fit is.
