I've just been reading a US Ford Fusion Forum where there have been a number of 2.3 to 2.5 upgrades there.
Of interest, they have noted that the Exhaust Ports on the 2.5 are sooo much bigger than the 2.3, that the 2.3 manifold does not have enough 'meat around the edges' to correctly seal against the 2.5 head. Discussions regarding the 2.0 manifold for the Miata do not seem to have this problem. But my thought was whether the Fiesta 2.0 manifold might have this issue too.
If so, a guy that goes by the name of Milan2008 on the Fusion Forums site has machined up and plate and is happy to sell it. This same guy has also machined up an adapter that allows you to fit a 2.3 throttle body on the 2.5 intake manifold.
Forum link
Since the Mondeo only ever seemed to ship with the 2.3 in Australia, this is all very likely to be applicable. I wonder if the Fusion never came with the Ecoboost in the US....?
Lukeyson