2008 Grand Marquis LS?

Wanted to know what size pipe are on a 2008 grand marquis it's a single exhaust and i want to convert it to dual exhaust and i want to get a Tru X-pipe from Magna Flow instead of a traditional H pipe. And which mufflers would sound better on this vehicle i want flowmasters im deciding between the Original 40 series stainless steal or Super 40 series stainless steal anyone have any suggestions thanks.