I'll put in my prediction that fuel relay replacement will do the trick.

My opinion about watching the tach to guess fuel or spark: If the fuel pump quits, because power is interrupted, as would happen if the fuel relay caused it, you won't see any hesitation on the tach. More to the point, you won't be looking at the tach until the seat of your pants tells you to look for a pull-off right now, and all the red lights come on.

And those lights don't come on until the engine stops turning and the alternator stops with it. All within a half second. Try it. Simulate by lifting fuse 7 while the car is running. See how fast the tach drops and the warning lights come on. Put some load on the engine (in drive if an auto with the brake on) and see how fast stopping the fuel pump stops the motor.

Back to my prediction. I just got done repairing some old k-jet relays I collected back when these cars still populated the pnp yards. I think they may have been the reason they were in the junk yards. One was beyond re-soldering, another the victim of some quick-fixer jamming the relay contacts closed.

Anyhow, it seems most have a burn mark on the bottom either at 30 or 87, that made many techs replace the relay but miss the relay socket. So many even believe the relay is somehow at fault for not being rated for enough current. Not true. The relay contacts are rated 3x the main pump current. But the socket's relaxed grip on the relay terminal was the point of high resistance and cause of the heat. The problem is the relay socket and the moisture that follows the wiring into it.



On the other hand, in my 79, I had a trouble 20 years ago where the ignition would fail. The eventual fix was as noted above, the terminals connecting the ballast resistor. Restart and die. You've covered this. The sudden stall, even at speed, can be a connector anywhere in the fuel or ignition -- even the fuse contacts themselves.

If you see any evidence of overheating on your old relay, pull the socket apart and attend to the female spade terminals. Check the crimps. Maybe add your favorite moisture excluding grease. Even if you don't see the overheating evidence on the outside, have a look inside.
--
Art Benstein near Baltimore

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