Ok so im buying some overlays for my gauges, and since im going to be in there and have everything apart figured id put leds in there. My only question is are the 73 or 74 bulbs? Ive been searching for a hour and keep finding both. Also behind the gauges there black and grey bulb holders, whats the difference?

 

The information center bulb is a bit larger than the gauge bulbs, so you can see the information display during the day (parking lights off). This bulb dims when the parking lights are on.