I have tried the LED's and agree with Michael King, until these lamps come in different colors, I am out. LED lamps for home use from companies like Philips are available in different Kelvins rating now that denote color, 2700K is warm white, 3000K is soft white, 4000K with daylight which is bluish. The instrument LED lamps available today are probably about 4000-5000K which is too blue for me to look natural in a 50 year old car.
I tested LED's in a Tiger speedo and a gauge that was cleaned up and repainted white inside with new 1446 incandescent lamps and have attached a picture here. I also repainted a can in various colors to try and color correct for the LED's blueish light and here are my opinions.
The most natural but most labor intensive solution is to take the gauges apart, repaint the inside cans gloss white and use 1446 incandescent lamps. The gauges are easy to read and look correct.
LED's are the easiest fix but you need to be OK with the color. They are also not really any brighter than a gauge that has been re-painted and re-lamped incandescent. Changing the inside can color does not fix the color issue.
When instrument lamps are available with a kelvin rating of 2700K-3000K and are dim able, your will have adequate light, color correctness and the ability to use the middle position on your gauge switch to dim then down.
