Or 1k with free shipping each, LOL. Found this in 10 seconds, might be able to find even cheaper with some real homework and not a 10 second google challenge.
http://www.amazon.com/dp/B007QBK0QU
Although the Z will cost more, just not sure how much. Hell, get me the hub offset for the center hats and I'll have a machinist build me a set if GM gets stupid with pricing.