Re: gutting the cats
Advice on getting O2s out, since you seem to be on a beer budget and you don't want to strip a wide band:
Try this cold first: PB blaster or other release agent, soak that sucker and leave it at least an hour. Then, buy an O2 sensor socket, TIGHTEN the O2 fist a bit to release the tension on the threads and then work it out a little at a time, adding PB or whatever regularly. If at anytime it feels like it's tightening up, STOP, go back in a bit and add more PB.
If they won't come adrift this way, do the same procedure when the pipes are hot. You'll need welding or other heavy leather gloves for this one, and long sleeves. The heat eases the thread interface lock and can make getting the part apart easier.
This technique is what I use to get seized and rusty nuts off the hot side of turbos for rebuild. There is no nut or bolt on planet earth more jammed tight than one of those. Most of the time, they'll wind right off if you do it this way.