I am not certain what difference there is from a 3.8 V6 or 4.6 GT as compared to the 4.6Cobra in regards to the fuel tank and provided space under the car. As with the Cobra having the IRS, there is not much room for experimentation. I have thought about that in the back of my mind prior to replacing the exhuast in my cobra. What would be cool is to have the pipes come straight back without having to bend out to the sides. What comes to mind by having a heated surface trialing behind the fuel tank sort of reminds me of the Pinto days when they blew up after being rear ended. At least there is a fuel tank shield on the under side of the car. I am not trying to rip your idea apart (only thinking out of the box for the moment). I think the redering is a cool idea. Does Saleen really have that? I have yet to see one that does, but then of course most of the Saleens I have seen in the more recent mustang styles were just decal jobs and not the prize Saleen I mistaken them to be. That makes me question if the Saleen uses a fuel cell position in a different location than the stock tank. As for the 3.8 and converting it to a dual exhaust, will increase the overall volume of the system so more bends may not be all that restrictive. I have seen similar concept in Muscle Mustangs and Fast Fords, but the exhaust was a very large oval which just about occupied the entire rear end. If it works, go for it. Sometimes originality pays off at car shows. Then again, since the mustang out-sells most sport sedans, we like to keep our cars personalized so we can find them in a large parking lot.