Well there they are on 18's so don't need 20's. Dr diff has assured me they will fit on my 17's, so no don't need 20's. No custom parts needed either...
For the SRT brakes, or the brembo 'style' brakes from doctor diff? The SRT caliper brackets bolt right on as well? Seems like it would be a more popular swap then, instead of using Cobra brakes for the rear and something else for the front. Let me know how that works out