The parts list can be confusing. You will need cobra Rear Caliper Mounting Flanges (these are the metal plates that bolt to your axle and have two holes to mount the rear calipers to). You need these because the cobra rotors are taller and these will give you the clearance you need as opposed to GT flanges. You will also need cobra caliper brackets (these are part of the rear caliper and slide over the rear rotor and hold the brake pads.) you need a cobra unit because the cobra rotor is thicker than a GT rotor. You can modify GT caliper brackets by grinding them to open them up a little. Thats what I did and it worked well and costs much less.
You will need to modify your existing porportioning valve and install an adjustable valve as per the website already mentioned.
You will also need a new master cylinder from a 94-95 V6, GT or cobra -also mentioned in the website.
I took my time and did mine, it wasnt too complex but it was alot of labor.
In hindsight, I would probably have just went with GT rear discs. The cobra units are only slightly bigger but they will cost alot more to install (specific rotors, mounting flange, pads and caliper bracket).
Good luck