Perhaps I am misreading or over-thinking the original post. Despite that possibility I thought it would be worth mentioning that for incandescent dash illumination bulbs being replaced with LED lighting, the LED lights are polarity sensitive. If they are not coming on when the headlight switch is turned on it is possible the LED lights that not coming on need to be removed from the circuit board and rotated 180 degrees to get the proper polarity.
Also, I am pretty sure I have read that LED lights can't be dimmed using the conventional headlight dimmer rheostat. At that, not all LEDs can be dimmed even with the correct non-Rheostat based techniques as they have certain voltage threshholds needed to get them to illuminate. I need to dig into this a bit more to see if there is a way to dim LED lights, specifically for instrument panel illumination. In the event LED lights are not coming on I would be making sure the Rheostat is not in a dimming position rotationally, as the LED lights may be Go-No Go in behavior when inadequate voltage is applied to them.
I think it is about time I consider replacing some 194 incandescent bulbs with LED lights just to see how they behave with a headlight dimming rheostat, and if indeed the Rheostat does not work see what can be used to reduce LED light output levels. On the other hand I bet I can dig out info by doing a deep Google dive into the subject.
One thing I have read about LED lights in general is how many of the ones with brighter light output can and will overheat unless they they are equipped with a heat sink technology. I find it hard to believe an LED replacement for 194 bulbs would run hot enough to require an integrated heatsink. So, yeah, time to begin playing with this stuff. Perhaps this can become a Winter project using a 12 volt power source in the house with a mocked up instrument panel, conventional Ford light switch, etc. I have not bothered digging into this subject deeply as I replaced our ***** light instrument panels with Dakota VHX instrument panels. I am pretty sure I still have the original panels laying around in the garage - I sure hope so. That would be a fun interest area to dive into inside the house this Winter.