If you're upgrading the exhaust on your alltrac, you should definately do a full 3inch exhaust. This includes a 3inch catalytic convertor. But for those of us that live in california, its not so easy to find a CARB (california Air Resources Board) compliant one. I recently came across a magnaflow 3inch universal CARB compliant cat for $200. I got it at kragen-oreilleys. The part number is 41409. Hopefully its the same for all other autopart stores. Don't see why it wouldn't be. Enjoy!