Cobra rear brakes are the same as the GT.
I would revise this to say the rear brake CALIPERS and BRACKETS are the same as on the V6/GT. The bracket on the axle is larger, pushing the caliper out farther to accommodate the larger brake rotor. I've heard that the V6/GT bracket may need a bit of grinding to clear the rotor, but I didn't have to on my Cobra conversion. I'm using GT brake calipers on the Cobra rear axle (the calipers were already painted) and the Cobra calipers on the front.