IF you are lucky there will be a paper tag still stuck on the end of the head from the factory with what looks like a UPC code and a bunch of numbers. That is the "broadcast code". I don't remember where I found the decoder, it was several years ago. Maybe even here, but Google IS great.

 

If the valve goes into a drilled hole in the exhaust manifold then just use the original HHR manifold

 

Ya, I have the choice of 2 engines, one with and one without. I also wanted to be certain there would be no other concerns and I wasn't sure if it was that straight forward, but it sure seems to be. The only other concern, is manifolds are not always fun to change in Canadian cars, so I figured if I have the option, I'll try to keep it simple! lol!!

donbrew, brought up a couple excellent points, that seem to be on the money, with everything I'm finding too.