I am swapping out a 305 to a 383 and everyone says get a cat exaust but what size tubing should i get. Want to stay street legal

 

Cat-back exhausts are all emissions legal, because they dont effect the emissions output of the engine. They just regulate the sound. You can use whichever one you want, based on your sound preference. How much horsepower is your 383 going to be making? 3" might handle it, or 3.5".

------------------
West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

It will put out 350hp min.