Been experimenting in my mad scientist's lab tonight...
I have discovered that the way to substitute LEDs for incadesant lamps in a 12v DC system is to wire as many LEDs as necessary in parallel each with their own dropping resistor. Not only does this work, if you use multiple LEDs and one burns out, the rest continue glowing.
A typical resistor value (for you soldering iron jockeys) would be around 220 Ohms.
Here is a picture and schematic for those of you who want to experiment, too!
'Ol Yellow Wheels before...