Probably a bit late now but in Australia the separation date between 240 and 280 parts(primarily suspension) was September of 1974. We never got 280Z's out here it was all 260z from 73-78. The only reason I know this is that every time I went into get parts from my (not) so friendly Nissan Dealer and from the steering and suspension place I got the work done was that I'd get asked what month(mines February)