Frustrating Caprice sometimes won't start

Where should I look? Here's the symptom: On occasion, if you start it and immediately put in gear, it dies and won't start again for a
couple hours. Spins motor, doesn't fire. Then, after a while, it'll work.
Now it won't start at all. Also - sounds like there is a click behind the water pump, when you turn on the ignition. Does this mean the opti-spark has died? Anybody else encountered this?
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