I was under the impression that the 280 cap was just as advertised cars like the skyline are advertised at like 280 but push over 300 at the crank (just speculation no real evidence) but as far as the Z goes its the same motor essentailly from US spec to Japanese Specification and in japan is advertsied as 276 but pushes the 300 crank ratings that our z's have. Not to mention that Nissan North America and Nissan Japan still operate simi independantly...