There is a set of Stage I Euro Springs on E-bay... The seller has them listed as fitting 240/260/280Z.... but they fit only cars made after 08/73...

Part Numbers

54010-N3502 and 55020-N3502

FWIW,

Carl B.

Link to the auction:

http://cgi.ebay.com/ebaymotors/1970-73-Datsun-240Z-Stage-one-euro-springs-from-Nismo_W0QQcmdZViewItemQQcategoryZ33582QQihZ014QQitemZ330210892934QQrdZ1QQsspagenameZWDVW

FWIW - I have the reproductions sold by Courtesy Nissan on my 240Z with KYB GR-2 struts. The ride and handling is good, but you will have to shorten these springs to have a normal ride height.