360 Were CA 360’s all delivered with MY2000 headers/cats/emissions?

Question about a bizarre discovery I made over the weekend. While installing my new Kline Inconel Catback, I first reinstalled the OEM cats to see how I liked that sound and volume level. Come to find out, the cats and headers that accompanied the car in a box from the previous owner were the cats and headers from a MY2000 car, as pictured and described in the WSM.
However, my car is 2003. The only theory I can come up with is that since it was a CA-delivered car, that those cars had to retain the more stringent emissions equipment from the MY2000 model? In my case, the cats and headers? I have all the service records going back to the initial sale, and none of them indicate exhaust work, until the prior owner had the Tubi headers and hi flow cats installed in 2019.
Any insights here?
Thanks

 

I was led to believe that only MY2000 had the air injection setup with 1 O2 sensor in the header, and 1 in the cat, with substrate on either side of it. When I was swapping in the OEM cat, I was told that I should have 2 O2 bungs in the cat, then shown a picture of such (shown below). I was confused, and wondering why my ‘03 had ‘00 exhaust components, as was suggested to me. The manual specifies only MY2000, but we all know the amount of oversights and erroneous information contained therein…
I’m just curious.
Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login

 

Well that will explain it! Exactly what I was wondering. Thanks!