Did the engine just die or did you get a fluctuation in the electrical system. By fluctuation I mean did the light flicker, the radio cut in and out, etc. Lights will dim when the engine dies but not usually flicker.

How long before it restarted?

Several things come to my mind right of the bat.
#1 on my list, Bad Ignition box.
#2 Bad Connection in the electrical system. Check all connection especially the bulkhead, wires to the distributor pickup, and the disconnect at the steering column for the ignition switch. Don't forget the battery.
#3 Ballast Resister going bad.
#4 Bad Pickup coil in the distributor.
#5 Coil going bad
#6 Fusible link going bad. Fluctuations/flickering is common. it should not be crispy or feel crunchy when you flex it.
#7 Wiring harness going bad. Check for crispy wires on both sides of the bulkhead connector, connecting to the Ammeter in the dash, and in the harness that runs along side the valve cover going to the Alternator.
#8 Bad ignition switch.

Hope it helps.