Don't tell the spammers making millions of dollars about that header trick.
Seriously though, I don't think a couple of headers will cause an email to become not spam. Google's filter is probably Bayesian, and considers the content of the message, the matching between the originating server and the reply-to address, the spam history of the originating server, any links in the message, how many times it sees the exact same message, how many people mark it as spam, etc.
So maybe it will get through to the first few hundred people, and then they'll block it.
Seriously though, I don't think a couple of headers will cause an email to become not spam. Google's filter is probably Bayesian, and considers the content of the message, the matching between the originating server and the reply-to address, the spam history of the originating server, any links in the message, how many times it sees the exact same message, how many people mark it as spam, etc.
So maybe it will get through to the first few hundred people, and then they'll block it.