The C36 has a performance exhaust with 3 inch diammeter because its a tund engine, the C280 doesn't.
I've got a performance system on mine which was welded to the C36 backbox. but my old standard piping was far too small in diammeter to fit to the C36 backbox, it would've had to be stretched by a massive amount to fit it on.
But i'm guessing you want the gain of power from the whole system, so i'd advise starting from the cat back and then welding the remainder of it to the c36 backbox. Its a perfect fit.
Adam