Something to add, cats don't just clog up all of the sudden and generally start to fail due to working harder than they're suppose to. Burning oil, running rich/lean, burning coolant all decrease the life of a converter. I can go right now to at least five of these trucks with 150k+ and still running fine on stock cats. Now that I have a circled the bush, here's my point, even if you remove the cats and program the rear O2s out, you may still have an underlying issue that did the cats in originally.
Here is some reading on catalytic converter operation:
http://www.aa1car.com/library/converter.htm