[Brant]

we put a 2nd warning light on our race car for just this exact reason.
we used a shift light (bright.. lots of volts though) with a blue cover on it.

the thing is that the alternator warning light is really designed to carry a very specific amount of current.

its more than just a warning, it is also the feedback loop that excites the alternator.

if you change the total voltage (by changing bulb size or adding bulbs) bad things will happen to your charging system

when we did ours we had to run a very specific resistor in line to replace the bulb and then used a relay to turn off an on the warning light.

LED's may or may not be safe since they draw so little power, but this is a delicate and sensitive set up.

be cautious.
brant