More testing done, since the car is currently sitting with no fuel tank underneath it right now. Pulled each gauge and tested individually except for fuel gauge. Happily, with the tank and sender removed, the LED warning light for low fuel has come to life. All gauges show life bench-tested, which rules out a load spike death. I cleaned the gauge contacts before reinstalling them.

This leaves me with two options: the cluster connectors themselves, or the bulkhead connector. I've pulled both cluster connectors, cleaned the terminals, and have made sure the contacts are good. How likely is it that the bulkhead connector has an issue?