I think the stock exhaust size is 1-3/4". What size do the aftermarket catbacks use?

My exhaust shop can do some custom work to eliminate the Y-pipe and rebuild the exhaust as a dual exhaust. What size piping would be best to use on the G? (with an R2C intake). Thanks.

 

Many aftermarket exhausts for the G are 60 mm piping which is about 2 3/8" ID.

 

Thanks for your answer, BB. But I should have phrased my original question differently. Let me try that again...

Does the typical aftermarket axle-back inlet have that same 60mm size? Wouldn't the size of the exhaust pipe have to match the muffler inlet to yield the best airflow rate. I know these cars are tuned for the ideal AFM and I don't want to screw it up, thanks.