3" TTI exhaust out the back
I had 3 inch on my 69 cuda when I got the car. I was very new by the previous owner, however I took it off and went back to stock. The 3 inch fit in there, but was really too big and touched the rear brake hose and other stuff. In my opinion there is just not enough room. Depends on what you want & if you are willing to put up with the extra aggravation.