The front cats are going to be really tight. I just replaced my rears with two small high flow bullet cats after both cats rattled...if you wait about 2000 miles the cores should turn to dust and blow out, but I will tell you the car was much louder and suffered a slight hiccup in power with them missing the cores. You can check eastern catalytic and they make a complete exhaust system with both fronts and rears and all pipes and you should be able to snag it for around 600.00, for us SRT6 owners it appears its off to mercedes for rebuilt systems at 2500.00.