Intermittent total loss of electrical

UPDATE: The problem hasn't resurfaced for a couple of weeks now. No way to know for sure exactly what fixed it (if it is in fact fixed), but my gut tells me it was a poor connection somewhere in the ammeter feed.
The things I've done so far are:
1. Verified that the bulkhead connector was not the problem.
2. Went through all accessible parts of the harness cleaning, tightening, and securing connections. Removed/replaced a lot of loose electrical tape. Used dielectric grease when appropriate.
3. Replaced ignition switch (the switch was sloppy and needed replacing anyway, but the switch alone doesn't fit the original symptom).
4. Replaced the ballast resistor.
5. Replaced the mechanical voltage regulator with a solid state replica.
6. Added a 16 gauge fusible link at the starter relay for safety's sake. The original had apparently been removed when they modified the ammeter feed to bypass the bulkhead connector.