you shouldn't need anything else except to get it painted if it isn't already. You can use your hinges and hardware for the latch and everything else. Does it come with the heat shield thingy. That is something you might want to know. You want one in so it doesn't discolor your hood with heat spots.
What year Cobra hood? 03-04? If so, then I think I remember reading that you'll have problems fitting it up because the 03-04 cobras had a hood that sat lower on the front fascia of the car. The front bumper is also shorter to accomodate this. I'm sure someone will correct me if I'm wrong.
I think that's when you have a Cobra bumper and GT hood, though . Like I said before, I think you'd have problems with a Cobra hood and GT bumper because of the way they line up.
there won't be any problem at all with an 03 cobra bumper and GT hood...the supposedly gap can be fixed in 5 min
see the reference thread on corral.net