The tank can be modified and you can avoid the skirt (I've got one modified at home fir this purpose now)...as I remember the european ones only run pipes to the rear so they avoid mufflers getting in the way, and the skirt hides the pipes looping all over the place. The modified tank route looses some capacity, and you need to carefully choose your muffler to ensure it will look right, but you can do it without a skirt and keep the mufflers at the rear of the car.
There was also someone who used a BMW or Ferrari muffler. The muffler itself sits under the bumper bar across the back and has a single inlet, with 4 tips, 2 per side outlet.