maybe worth consulting a local exhaust specialist.
we have one up here (worcester) that will custom make you an exhaust for about £300 in stainless steel, including fitting. you can even specify what you want it to do, eg side exit, twin tails, quad tails etc....
by the time you have bought the tube, cut it, measured it, bent it, welded it, re cut it, re welded it and finally fitted it it may work out cheaper to have one made....just a thought