I know that the 79 model cj engines didnt come with the cat system hook ups. But as sunder and others will/should say i believe if it has it in there stock it "should" have it. But seeing as how its 86 and older when emmissions laws went into effect the cat is not "required" I have a 79 engine in my 83. The old exhaust system had the cat in it but no hook ups for the engine. So when the cat got clogged i just put a pipe in it. A muffler is a nice thing to have though. I have a good little flowmaster on mine and it sounds nice. Not to loud but clean. hope that helped some <img src="/forums/images/graemlins/kewl.gif" alt="" />