IMO it's a lot of work to put a zetec, turbo'd or not into a mk5 Fiesta. You need a lot of custom parts, especially if using an MTX75 gearbox.
As for brakes ST170 callipers will work on the front, just need to enlarge the holes on the hub to take M12 bolts. The rear disc conversion isn't too difficult either. A little more tricky if you want to retain ABS as you need to get the Tone rings from the drums machines onto the back of the stub axles.