First, let me say I cannot answer your question.
I have never had a set of headers that "just bolted on" without any modifications. They all need a little tweaking, maybe it's just a bolt hole, or some extra room around a spark plug for a socket. My point is, why would you buy headers that are already ceramic coated before you try them on your application? If you need to make any modifications you will be sick. How about the "Y" or "X" pipe? Would you not want that also coated?
I'm a big fan of ceramic coating on exhaust systems. It keeps the heat inside the pipe, and has less radiant heat. My last ceramic coated exhaust system was done Tip to Tip in Satin Black and look like new after ten years of use.
I would fabricate the entire system, make your changes, pull it apart, and have it coated. Many of the larger volume powder coat shops, now have added ceramic coating facilities.
John
Palmer, who did you coating on exhaust, i am going with explorer manifolds and want to find a reasonable place to get them coated.