jamesinc Hmm I don't know anyone (commercial) in Sydney who has that kind of expertise. You could try talking to Stu at VolteK, he mostly does 1990s-onwards Volvos but he may be able to help or point you in the right direction. The main thing is you will want to source a 16V head. As of the last couple years, you can now also buy cast 16V high-mount manifolds: https://www.thekangaroosteam.com/shop-1/volvo-redblock-16v-turbo-manifold-t3-twin-scroll
