I never drive the Corvette at night, but I do occasionally need to use the instrument cluster lights (when driving in one of Sydney's many long tunnels for example). Pulling the headlight knob out half-way turns on the park lights, tail lights and instrument lights — a feature I didn't discover until I had owned the car for a year!. The instrument lights produced a feeble, yellow glow resembling candle light. I'm not sure if they were like that in 1965, but it was barely bright enough to read the speedo.
Replacing the original incandescent globes with LEDs is a popular upgrade, but some owners feel that the result is too bright, too 'modern'. Look at the photo of the rear of the instrument cluster above, you'll see that there are 9 globes marked 'PL' — these are the instrument lights. In addition to these 9 globes, there are 5 more for the turn signals, high beam and brake warning lights — a total of 14 globes.
I decided to try replacing only 4 globes with white LEDs (the ones circled in yellow above). I could (just) reach these globes from under the dash, so there was no need to remove the cluster (and risk damaging something in the process).
The result was just what I'd hoped for. Bright, even lighting across all the gauges, but with some warmth from the remaining incandescent globes. The dimmer switch on the cluster lights works perfectly with the LEDs too.
I ended up using the same LED globes in the clock and radio as well, so all the instruments are now illuminated evenly.