On 240Z's the coil you are talking about is usually mounted right below the coil. The coil is normally mounted on the left fender in front of the wheel hump, and it is usually mounted horizontally (i.e. the coil body is horizontal,with the top facing the front of the car). The resistor is usually mounted right below the coil.
I'm not sure on ZX's but I'm inclined to agree that they wouldn't have one since they have electronic ignition and the resistor is for the tachometer to read the pulses of the points and coil. In fact if you've changed the distributor on a 240 all the tech write-ups say to remove and pitch that resistor.
Hope it helps