the 09 aveo, with the 1.6 eco-tech (in the us). header would be nice, i think it has the flange of the other header in a pair of headers picture you posted. but a picture and not measurements does no good.
ive not seen any pics of the 09 manifold yet, without the heatsheild, the lengths would problay be a little differenet but then again, they might be the same :P
without removing the heat shield the flange is different because we dont have the extension on the end, and it looks like triangular bolt pattern around each pipe.
I would love a header for my 09', but we can't really run them here. Your car will never warm up at -60*F. It's bad enough in the winter I have to cover my whole radiator with cardboard.
couldn't you put a header on the then reattach the heat shield? i know some vw headers already come with the provisions. but the you would have performance without sacrificing the heat riser.