Swapped in white LEDs into my cluster, and pulled my seatbelt light (since I swapped to B14 belts.)
I saw that there was no bulb in the gas light, so I put one in.
I also saw that the "black box" on the back of the cluster wasn't plugged in. That turned out to be the buzzer that rings when the door is open with either the key in the ignition, or the lights on.
I then realized that the gas light was pulled because otherwise it comes on with a full tank, and the buzzer was unplugged because it's annoying and sounds like it's dying.
This would be pretty cool -
https://youtu.be/gcPJdwb7xmo?t=76 edit - I found one from the junkyard!
As far as the gas light goes, the true fix is probably this -
Problems & Fixes: Inaccurate Fuel Guage
But I'll probably just remove the bulb and fill up after 250 miles.