Probably someone has got confused with the various Nissan 4-pot calipers which are similar looking to the Hilux ones. See http://www.princeton.edu/~asad/zbrakes/ for a comparison of the 2 different ali and 1 iron caliper used on different 300ZX models. Incidentally, these alloy calipers seem to pop up for sale fairly regularly for as little as $250-$300 a pair.