A pre-cat system has a cat at the exhaust manifold dumps and one more cat down stream on the exhaust. Many of the larger newer V-8'* have them.

Can you take some clear pictures of what it is your are looking at? A couple of us are kinda confused and we want to help you, but not give you bum info on what we think it is.

I can try but it may be a couple of days before I can get to it.

We will be here!

What would happen if I replaced the converter, removed the resonator, and welded an o2 bung into the exhaust pipe? Will this work or is this just a stupid idea?

That will work just fine. But as I said, that will make the tone more raspy.

You can replace the converter. I did mine and went with a Goerlich Hi-Flow. I also removed the resonator and kept the rear O2 sensor. The resonator just removes some of the raspy sound that V-6'* seem to produce. This is what my exhaust sounds like with Magnaflow mufflers Magna Flow Mufflers and Hi-Flow Cat on Flickr - Photo Sharing!