Really like this manifold research, are the bolt spacings similar at all?
If not I think I've seen people offering waterjet flanges for $50-$100 Could supply drawings of each and have a hybrid made up, best of both worlds, or continue boring out the mx5 one to fit.
How does the rest of the manifold fit in the engine bay, there is a lot of room there, but no risk of it hitting the frame rails there at all?