The adapters are 2 piece (2 inches total) and can be gotten in any pcd desired.  
Ross..I don't think that they are Z specific, however, I am sure that they can machine them a little to customer specs. 
Dan Juday.. I don't know anything about the guy except for the short conversation I had with him at the swap meet.  He had a HUGE assortment of adapters, spacers, lug nuts, valves...etc.  The finish on the spacers 'looked' very nice, and when I asked him what material they were made from, he couldn't be specific, except to say " the same as aluminum rims" 
If you want me to call and get details (free call), let me know. 
Tim