Don't quote me on this, but if I recall correctly, the biggest disk was 300mm and that was with slimline (possibly Wilwood or Hi-Spec) calipers. I think I could have possibly gotten away with 315mm disks if using the EsCos Monte rims - but none of the options were suitable for my power..... hence I've had to go bigger wheels to fit Ap's under.

Std EsCos calipers & disks are still capable of hauling up a stage 3 Cossie, so may still be an option on a Fezzy? FiestaTurbo.com will no doubt have people who have tried various braking/wheel options, so probably worth a visit.