1972 Oldsmobile Cutlass 1972 Cutlass intermittent stall whi

Have a 1972 Cutlass 350-4V. 210k miles. Orig engine.
Yesterday, drove about 1-1/2 miles, stopped at the store about 15 min, started up, drove away. After 200' car started dying out, then died. Took off air cleaner, moved throttle, weak streams, checked for loose wires, didn't see any. 5 minutes later started up, ran fine. Drove home.
Today, drove 9 miles with 3 stops, 1st two 5 min with no problems, last stop 20 minutes, started up, drove off, after 500' started dying, pumped the pedal, it ran another 40 feet, then died. No backfire, but there was bit of an odor like when timing is over-advanced. Took off air cleaner, didn't look like any streams from accel pump. Cranked it periodically to re-start, no luck. Let it sit about 10 minutes, started right up, ran fine, drove about 1 mile home.
Outside air temperature has been about 65å¼, so it doesn't seem likely to be vapor lock.
Car has Petronix ignition under distributor cap.
I didn't have anyone to crank while I checked for spark when it had died, so I can't rule out ignition side problem, though I don't know what ignition side part would work fine, die, then come back again.
I tried to duplicate by letting it sit, restart after 15-20 min, but ran fine. Car well maintained & never left me stranded in the 27 yrs I've had it.
Ideas on what might cause this intermittent problem? Thanks