converter

Ive researched this alittle bit, but i wanted some input from the guys here. Ive got a liberty that just got new tires, upper and lower rear end control arms, shocks, diff fluid, u-joints, the whole 9 yards. But i still get a rear end vibration at around 40-55MPH. I haven't tried highway speeds...

So my catalytic converter on my 05 Libby went out and I need to replace it. I am looking for something that does not require me to weld in a new one. Also I was going to go with the Mopar, but that are no longer making it, so it is not an option. What are some of the best options I can do with...