There is no replacement for displacement, get a 2.0 and have done with it. Silvertop will be easier to fit but getting one won't.

You could install an st170 or standard Zetec with Oem bits like inlet and ecu. Pats Immobilizer isn't hard to use. For £500 but it will take some work making bits. But you won't turbo it for that money.

Wiring info.

Zetec

http://www.locostbuilders.co.uk/view...php?tid=179921

St170

http://www.locostbuilders.co.uk/view...php?tid=190440