After driving 80mph for an hour, the engine started to sputter as if I lost spark in one cylinder. The sputter lasted for about two minutes then disappeared. Approximately 10 minutes later, it returned. I was not far from my Dad's place at that point so I made a detour and did some diagnosis once there.
The car would not restart once I turned it off. After cajoling Dad to take a break from the White Sox game, he came out and took a peek. As I cranked it, he noticed quite a few sparks emanating from the coil and dancing over to the coil mount. Seems the casing of the coil had a hair-line crack. Plastic lives a hard life under the hood of a car. Eighteen years was all it could muster.
Once I obtained a replacement coil from the neighborhood auto parts emporium, the old Stang fired right up.
This has got me thinking about what will be needed in terms of a new engine wiring harness. I've found some for 89-93 and the ones that say they are for 94-95 require you to change over to an 89-93 distributor and TFI. If I do that, I won't have a 94-95 anymore! Perhaps I just need to do some more searching on this new fangled Internet thing.