I have seen a good amount of discussion on previous searches for and sales of Z hubcaps and seen how spectacularly well some members have revived their old hubcaps. There is currently a set of four listed with only 16 hours to go that might be of interest to someone - currently bidding is at AUS$61 or approximately US$45:

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=4622981160

EDIT : Sold for AUS $101.50 Approximately US$75

Those aren't in very good shape and would take a lot of work to restore. If they were the "D" hubcaps, however, they would be worth buying & restoring since 'D" hubcaps are so rare and valuable ("D's" were only available on '70 & '71 240Zs). Here's a nice set of "Z" hubcaps, complete with the wheels on Ebay:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=8046511149&sspagename=STRK%3AMEWA%3AIT