true duel exhaust is two seperate pipes which never cross paths. if you want true duel, you have to scrap your whole exhaust system (minus the manafoilds) and run new pipes.
the answer is yes, or an h pipe. you can buy a h pipe or now from laurelmountain mustang an x pipe that runs from the manifolds down and under the car. from there you would need to buy intermediate pipes, mufflers, and tailpipes if you so desire and all the neccessary hangers. so like 6stang7 said, ud basically be replacing your whole exhaust. for the money, i recommend taking the car to an exhaust shop with your favorite mufflers in hand and having them weld everything up and doing a custom exhaust for you. will be about the same price if not cheaper and will work better, unless of course u are worried about concorse correct issues.