Thanks RCMAN46 for confirming that.
I looked again at our Series06 wheels and I don't believe a metal valve stem is going to be an option with these wheels. Uugh... The aluminum wheel seems to have a half inch or so plastic outer coating and the current regular valve stem is recessed down into a cavity that I don't believe (but not positive) can hold a metal valve stem nut/washer/grommet. The recess is about a half inch deep. I took a couple pics.
http://i.imgur.com/0oXRgQmm.jpg
http://i.imgur.com/gvS3d3zm.jpg
All input greatly appreciated. These wheels are the old 5 x 4.5 bolt pattern so one thing that comes to mind is possibly looking for an old set of GM steel wheels.