Just ordered a set of Kook's long tube headers stepped to 1 7/8" along with their 3" ORY. My car used to be my brother's before I bought it from him, so I'm not 100% sure about the exhaust. I believe he has a flowmaster muffler welded in place of the stock muffler and NOT a cat-back system. So my question is will a 3" ORY mate up with the stock exhaust system?
BTW I'm a new member here...lookin forward to becoming a regular

 

It can be stepped down to the stock exhaust size (2.5 I think). Any good exhaust shop will be able to do this. I have a 3"ory to a 3" cutout, then stock pipe behind that.

 

3" ORY is apparently too much for even a 3" catback. Get a 3"-> 2.5" reducer and get a 2.5" y-pipe if he's keeping stock exhaust tubing.