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.

The MM kit has brackets for the rear hoses, these replace the brackets spot-welded on to the factory hoses, which is a good thing. The kit is missing the factory bracket for the center line, but their instructions explain how to re-use the factory bracket. The brackets help keep the hard lines from flexing as the car moves around.