I checked in Google, they accept <g:availability>out of stock</g:availability>
http://www.google.com/support/mercha...r=188494#other
However, I don't really know the search results will include 'out of stock' items or not.
The reason to include 'out of stock' items in the feed, is to let customers know items may back in stock later.
I will try another <g:availability> value 'preorder', just using find and replace with some text editor.
Let see search results will include 'preorder' items or not.
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