My opinion on the California smog inspection is that many smog stations don't care that much where your cats are during the visual inspection, as long as they can see the cats and the car passes the tailpipe sniffer. Because if you pass the sniffer, you must have functional cats somewhere, right? Of course I wouldn't install Schmiedmann or Magnaflow headers with cats then go tell the smog guy about them, because then he might be required to ask for the CARB number and fail you when you can't supply one.
I think the smog computer tells the operator what equipment should be there for each make/model/year of car, but not where it is. So if your car is supposed to have an EGR valve and secondary air pump, the printout says those should be there, but doesn't supply a diagram showing where they are. Of course, I could be wrong about this.
My other concern would be that maybe a 49-state legal header/cat combo might somehow have cats that are not quite efficient enough for the California tailpipe sniffer standards. Did Magnaflow make these 49-state legal because they couldn't pass California emissions standards, or simply because it was too much hassle to get them CARB approved?