I have a 2005 GMC with a 4.3L V6. it keeps poping up with a code of po430?

I want to replace the cats on the truck I have already replaced the o2 sensors but the code keeps coming back So my question is. The truck was bought in California and I live in Colorado now Can I put the federal cats on them or do I need to put California legal cats on them. The price difference is huge the fed cats are only 80 or 90 and the California cats are 295 each.
 
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