I have 18x10 and 18x8 both +45 offset. However I am using a spacer in front. The correct size for a 300ZX is 18x10 +45 offset and 18x8.5 +41HD.
Also Racing Hart M5s are the same size and have a very deep dish. My rears are only 0.5" deeper than the M5s. However my edge of the center folds in not out so it makes it look even deeper.