1.8 zetec head has smaller combustion chambers than a 2.0L so you would end up with high compression. Manifold flange should be the same though, as Ford uses the same part for 1.8/2.0l focus's......

Ah just saw you said 'the ally one' - that'd be a 1.7/1.6/1.4/1.25, and is the Ford/Yamaha Sigma / Zetec-SE. Different engine completely to the Zetec-E that is your 2.0L!

Head from a Zetec-SE will never fit a Zetec-E in a million years!