Okay, let me start off by saying that I'm a huge fan of LEDs -- as proof, I'm the one who converted *all* his car's exterior lighting (except headlights) to LEDs by handwiring literally hundreds of LEDs onto circuit boards inserted in the light housing (examples below). You may either remember my old posts here, or my extensive article published in Rolling, "Converting to LED Lamps", 25(2), March/April 2007, pp 34-5, 37.

That said, however, I have to caution that LEDs have one major drawback compared to incandescent bulbs that may apply in your planned use. LEDs have directional emission of their light. Even the widest beam (and with that the lowest luminosity) LEDs have a limited spread of light compared to a filament that emits in all directions, and because of that I think that you might (and I'm admitting that it's only a "maybe" because I personally haven't looked into this) wind up with shadowy areas across your instruments. One of the acknowledged drawbacks of the 240's black-faced gauges is that for many folks they have to keep the rheostat cranked up to read the gauges (a solution is shown farther below). You may find that with LEDs, some areas of the gauges will be even more poorly illuminated. And while you can get LEDs with different beam angles, the brightness is inversely related to beam angle.

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Some illustrations of my handiwork:







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If you have a problem with poorly lit OEM black-faced gauges, Dave Barton made up a set of much brighter faces for my gauges, shown below. I find that these, their attribute being the bright face, are easy for me to see (and I'm an old geezer, retired, with expectedly poorer night vision than you "young'uns" :-) with the standard bulbs and the illumination rheostat set only midway):