I would highly recommend just getting a little black overflow from Jegs. They are really cheap and much smaller and cleaner looking than the huge stock one. Just a thought.
They are not exactly the same. The tank will fit in the same place, but the V6 tank does not have the notches in the top to fit the Low Coolant sensor - it only has a plastic cap. Of course, you can do like I did in my Cobra conversion; you can notch the plastic neck of the V6 tank to match the GT, and it will work perfectly. It's a bit of work, depends on how perfect you want it to be. But it will work.
They are not exactly the same. The tank will fit in the same place, but the V6 tank does not have the notches in the top to fit the Low Coolant sensor - it only has a plastic cap. Of course, you can do like I did in my Cobra conversion; you can notch the plastic neck of the V6 tank to match the GT, and it will work perfectly. It's a bit of work, depends on how perfect you want it to be. But it will work.