I think there is a slight over reaction. The alloy selected is what has been recommended. Having spoken to several people tonight I'm confident that the alloy selected will be sufficient.

If there is another option up for sale at similar costs but with better properties then it will be selected and at the very least considered.

Otherwise, the company in concern has done numerous engineering projects including many for performance race engines and they recommended this material so I'm okay with their selection.

In all honesty going by the quality grade of some the metals used in Datsun engines, the alloy used in the inlet manifolds couldn't be any better than what has been selected.

If you have any objections in material selection please PM me and I'll prepare your refund. Having said that, I'm willing to put my neck on the line and insist that this be the material. It is more than sufficient and it is certainly suitable.