So I’ve been doing a lot of searching and reading as I’m trying to put the pieces together to build my turbo setup . The engine is currently in the machine shop being pinned and half bridged. I am wanting my turbo to sit higher and more forward than the typical turblown cast manifolds that are made for the fc. Now my real question is what kind of fitment issues will I run into if I decide to order one that is made for the fd chassis? I’ll add I have a g35-1050 Garrett- v band inlet. I know I’ll lose some reaponse by going with longer runners. But I have a vision of where I want this turbo to be placed in the bay. I’ve found similar topics but not really answering my question . My other option is to have it all custom made by someone local but it would be nice to gather the parts and then start the build

 

the change from the FC to the FD, Mazda changed the angle of the ports. if you picture the lower intake as an L shape, everything up to the Cosmo has the ports just like that. the Cosmo and FD change the port angle.
this gives them more room for turbos closer to the engine.

sooooo the typical FD manifold has the turbo closer to the engine than the typical FC manifold. or conversely the FD manifold in an FC will put the turbo in the intake, a bit.

there are ways around it, the easy way might be something like a Greddy T78 manifold, which is setup for a big turbo, and then use a smaller turbo
people also buy an extra header flange and use that as a spacer.