not to throw out your question but are you sure its your convertor? seems unreasonable for a 2.5L motor to clog up a cat that quick, how many miles are on your jeep? if you are positive its your converter consider replacing it with a performance on (can be easily found at summit, jegs, etc). If your goal is to save money then I dont see a reason why you couldnt just pull one off another jeep (assuming pipe size and cat length are the same), just make sure its not clogged because that will kill your performance. Good Luck
A stroke bolder, a pinch better.