Yes, calibra pistons, a new adaptor welded onto the ERST or FRST manifold to make it fit the Zetec, the FRST mapping and it will run. But it surely won't make much fun, especially with that dinosaur of an turbo called T3.

Use a full Zetec engine, they're all not too expensive after all. (maybe you're lucky and you find a Focus RS one out of a crashed or a Cosworth conversion )
You can keep the whole cylinder head with the whole valve train, will work fine on turbo use, too. Burton sells accralite pistons, 125 GPB each. Not too expensive. Maybe you can get your hands onto a Focus RS manifold and Turbo (don't know if they fit the FBD) your you buy some special made parts. The real expensive parts - when you want to have fun - are a proper turbo (such is the GT28 focus RS item) and a full mappable ingnition and injection system.