Hey guys,
I know this may be a little late, but..... You don't need CATS, unless you're worried about being caught durring emisson test. I know this cause i just do. Me a friend rebuilt his Trans Am over the summer and he had to run a new exhast on it cause he put headers on it and didn't feel like installing CATs. So he designed a true dual system without cats. All you do is install the first O2 sensor in the bung on the header, the one before the CAT, because thats the only one that matters. The other one just makes sure that the CAT is working correctly. To get around that, just make an O2 simulater for the second sensor. Pretty sure everything you would need is avaible at your local Radio Shack.
http://mkiv.com/techarticles/oxygen_sensor_simulator/
Above is a link of how to make one. While i'm not 100% sure this would work. This is probably what i would do if you dont want to run a CAT or hook up your second O2 sensor due to it being too short.
Later, Pat