Wow, that's dedication. Not sure I agree/understand why the O2S placement is no good. What makes you think it'll overheat in its present location? If you do stumble on that Australian site, gimme a shout, willya?
I read a lot, and after these headers were built (timing is everything in a deal like this...) I discovered that everyone that WAS anyone, was recommending that the O2 sensor be located in the post-turbo (downpipe) section of the exhaust system. I got to asking around, and experienced, knowledgable, people like Gerry, at the G-Pop (turbo) Shop told me of the possibility that excessive exhaust gas temperatures could damage the sensor and it could become a two (or, more) piece missile, destroying the vanes of the turbo in the process.... Who am I to argue with folks like that???? I am 72 years old, and have been hot rodding since I was 15, but I have never had experience with turbos, and their various appurtenances.... I am an old man, but still, a turbo neophyte!
I will try to find that Aussie header for you, now...