This is a super old post but I'm going to fill in some details for anyone that comes across this like I did.
The high beam indicator bulb is the same size as the two turn signal indicator bulbs and actually the size as both the cigarette lighter bulb and the glovebox light bulb. These are all T1.5 or #74, something like
this [
superbrightleds.com] fits well. LEDs are sensitive to polarity so if it doesn't light up swap the orientation of the LED and it should work. It's quick and easy to get to the gauge/instrument cluster, the cigarette lighter, and the glove box lights. The high beam indicator and turn indicator lights just twist out and you can pull the bulb out of the plastic base and swap in the bulb.