The Zetec-SE it currently has fitted and the Zetec-E either in 1.8 or 2.0 guise are completly different engines, it's not worth the time nor the expense in doing so.

A few basic things, the inlet and exhaust are on opposing sides to start with and so you need to change the exhaust, you then need ECU etc, theres a whole load of other things to, IMO better off just having the engine rebuilt or replaced with a equivilant.

To add in the real world at least in standard tune anyway, it's a known fact there is very little difference between the 1.6 and 1.8, acceleration is around the same although obviously the 1.8 has better mid range grunt and after you done so you would have +15HP at the best for your effort as this is the power difference between the two.

Martin