[Rob Doe]

Spark at one plug isn't strong enough evidence. I would pull the coil wire out of the distributor cap, use an insulated pony clamp to position the wire 1/4" from a clean head nut, make sure the coil wire is full up into the coil secondary terminal.

Parking brake set, tranny in neutral, ig switch on, stand at the left side of the car and use your hand to engage the starter switch. Turn the engine over and you should get a clean, snappy blue spark on every compression. If you only get a weak, yellowish white spark, or only an occasional spark every few cylinders, suspect the primary ignition, i.e. points, condenser, unintended current draw, coil etc.

If you get a good, snappy blue spark on each compression, I'd check for fuel as stated above.