The Y-pipes are identical the mufflers for the GT and 3.0R are slightly larger but share the same mounting locations.
The tips are also different. Other than that you gain nothing by swapping. There are no gains, Catback wise, for a stock 2.5i the exhaust note will be virtually the same as well.
I have a stock LGT CBE on my 08 2.5i for the past 7 years.