Pretty much everything but the headlights are LED here and my dash lights dim almost normally, but once the voltage gets down pretty low they cut off when the incandescent bulbs would have dimmed a little more.
I run a 12v to 3.3 volt transformer chip off my dash lights circuit from the headlight switch/dimmer and power the multiple LED's in my dash and gauges.
This way the transformer allows me to add more raw single LED's anywhere if I want more or better light in specific area's of the dash and gauges, like when I added a clock that matches my other cluster gauges. (Drilled a small hole in the case and inserted the LED.) then added it to the 3.3 volt circuit. (now the new clock light looks like all the others and dims with the rest of the dash and gauges.
As far as tail and brake lights, I replaced my OE backup lenses in my four lens bumper with matching tail/brake lenses and doubled up on the brake and turn lighting by tying them to the two original lights.
All four lenses light with brakes, two on each side for signals and just the outer two for tail lights.
For tail and brake lights I used 4 of the Superbrite red 12 LED bulbs separated from their sockets and mounted the LED section inside the bulb housing facing directly rearward.
(Dart has angled sockets so I just soldered about 3 inches of wire between the bulb socket and the LED section so I could face them straight back). and a dab of RTV keeps them in place nicely.
3 years so far and not one burnout anywhere, and they use so little amps my dash or headlights don't even think about flickering when the four brake lights come on.
Obviously much brighter than all stock bulbs also.
The last little trick was to tack a credit card sized lexan magnifier inside each lens that magnifies the 12 LED's by 100% so they fill the lens more fully instead of just having a round spot in the center of the lenses about the size of a tennis ball.
This is the kind of stuff that happens when I am bored and want change something on my car.
I like high definition gauges and lighting so you can see the gauges lit on the bench at full power (3.3v), and the full assembly in the car during the day unlit.
Man, some day I need to get rid of that column gear indicator.
