I was kind of looking into this before. Now I'm by no means an authority on this, but this is what I gathered from my mud/google searches.
The first O2 sensor is before the cats, that is what the computer uses to determine how the truck is running. The second O2 sensor is only used to check if the cats are working properly. There are several O2 sensor simulators out there that generate the proper signal of a working O2 sensor. So you should *in theory* be able to remove both cats, splice in that simulator in place of the second O2 sensor (the first one you need for sure), and it should (could?) work.
I had ordered one of those sims off some guy on ebay in the winter, but it never ended up at my parcel place, or they lost it. And I haven't looked into it too much since.
Thats how my rig is setup up from the front O2 sensor its all pipe and a magnaflow muffler turned down inside the frame behind the axle. My EGR system is also capped off. I'm looking for someone who can tip me off on a worthy simulator for the rear O2 I've been driving it the last few months with the rear unplugged. It breathing much better these days and throttle response has improved
