The wheel can be widened but because of it's design you'll be forced to increase the offset as you increase the wheel width (unlike a 3-piece wheel). You'd be better off buying 18x9.5+37 wheels all the way around.
"The 300ZX Turbo is a dance; it's a song; it's rolling, roaring automotive art. There is no color that doesn't suit it. There is no mood-lifting chemical substance it can't replace." - Automobile Magazine