I have the 320 mm kit with standard calipers from Reyland. But the only reason I have that is because my wheels didn't provide enough clearance for 4 pots. All 4 pot calipers require at least 5.5 to 6 clearance between the disc surface and the inside of the wheel spokes. But reading you have Comps that's probably not a big problem. So E38 calipers could be an option. But you'll probably need a custom disc. The Focus RS discs don't fit the 4x4 due to the low disc offset on the 4x4.