Part Replacement Questions for Non-Stock Engine
 

I have a '99 Grand Prix GTP that has an engine out of an '04 Impala SS. I need to replace some of the sensors, and I started wondering what sensors I should put in. I need to change the O2 for sure, but the '99 shows a different part number than the '04. I was thinking that since the engine management and PCM are from the '99, would I use sensors for a '99?
Any advice would be great, my O2 is throwing a code, and when I scan it, it stays at a constant 455mV.