I popped mine out today to have a look. Is this what yours looks like?
I'm not sure what to make of the sweaty free-balling Christmas ornament second from the right. The drip says some kind of fluid is involved, and the color says it's urgent, but I don't see anything indicating heat. The '87 service manual shows a fuel filter light in the warning lamps section, specific to the SD25 diesel. I suspect that's what this is supposed to be. Maybe the bit at the bottom is supposed to be a sediment bowl? Naturally the manual only shows the circuit schematic, not the picture that the bulb lights up. The manual also shows a glow plug light, but nothing about that idiot light says "glow plug" to me (not that it really screams "filter," either). There is a bulb in that slot, and it's wired to the plug on the back of the surround, but the dash harness that plugs into it is not pinned for either of this bulb's wires.
The left side has two idiot lights for the auto trans (O/D Off and Power), one blacked-out idiot light slot with no bulb in it, and a low washer fluid light, which does have a bulb, despite being marked Canada-only in every service manual I've looked at. I did not chase the wiring to see if the washer fluid light or the empty slot are wired in the dash harness, but I did see that the dash harness plug has five pins, which is more than the two lights for the trans should need. (I'm also curious whether the manual US-spec trucks have a different rack of idiot lights for the left side, or whether it's just completely blanked out.)