lbcgav noted: *** Replacing the meter lamps with LEDs is a bit tricky because you're going to change the color of the meters by doing so. They usually end up looking more purple. I've simply stuck with the original lamps in both my MC2205 and my MC7270. ***
Personally, I agree with this, and not just because of the possibility of changing the color. LEDs are DC devices, and on older equipment like this, the lamp supplies are often AC. LEDs can create electrical noise as they switch on and off. To make matters more complicated, on later Mac amps, the engineers designed regulated AC supplies to keep the meter lamp intensity constant regardless of line voltage variations, supplies which assumed standard AC incandescent lamps were what they were driving.
Granted that this varies with the individual, but one other reason I dislike LEDs on AC supplies is that they flicker, like a computer monitor set at too low a refresh rate. This literally gives me a headache after staring at a component's front panel for more than a few minutes.
#259 lamps are still readily available at reasonable prices-- I'd go with them for your 7270.