430 Headers and oxygen sensor question

Sorry if this is a dumb question. I'll be getting some headers here soon and despite the plethora of information on the site about headers and whatnot, I haven't found any posts that address the oxygen sensor part of it, or maybe I've just missed it. As a technician, I'm always used to a cat with one upstream and one downstream sensor, however given these vehicles have the precat in the header, does the front sensor require the spacer in an attempt to keep the check engine light off?

I'll be picking up the big daddy spacers with the small "cat" integrated, but I just want to make sure that this spacer goes in the front location prior to the actual main catalytic converter.

Thanks in advance!

 

I was hoping it was the same as usual, it was just a small part of me that figured since there's a precat and the main cat, with the upstream sensor in between them, that there may have been a possibility of the spacer going on the front. But all good, spacer will go on the rear downstream O2. Thanks