Signal for spark is relatively linear going from the ECU driver circuit, to the ignitor, from the ignitor to the coil pack. If you have a known good ECU, you really only have two things to check other than the wiring and the spark plug wires themselves. Fortunately, both the ignitor and coil pack are cheap and easy to swap. I would do this first however.
Take the ignitor harness clip and unplug it. Look at the ignitor itself and it has letters on it which correspond to the ground, tach, and spark in and out. Check for ground at the corresponding wire on the harness. Without an oscilloscope, you won't be able to accurately read the signal to the ignitor for the positive, but you should be able to tell if it is there. If so, grab a dummy light and check the wires themselves.
Basically, confirm everything you possibly can, then eliminate things individually. If you find no signal going to the coil pack from the ignitor, but have voltage going in to the ignitor, new ignitor. If you have output voltage to the coil pack and no spark at any plug end, new coil pack.
Subsequently, if you do confirm, and I don't mean just guess, it is either of these things, I have spares here in the garage and can send you them gratis if you pay shipping.
/brox