You can use an LED, add a 470 ohm resistor and all is well. The reason I specify incandescent is you get more even distributed light from a single bulb, the LED is more focused at a point. It also takes one less part, you don't need the resistor. 
The Super-Chuffer includes a diode to protect against reverse voltage, so just a resistor is all you need for the LED.
For the ground light option of the Chuff-Generator, I use surface mount LED's on tiny PCBs. This is the board I use, I cut each individual LED and then glue them in place and wire them with #30 wire. Ground lights off the Chuff-Generator work just like the Super-Chuffer cab light for wiring, they just pull the lead to frame ground through a diode. Again, I just tie these to track power and string all on one side in series with a resistor for current limiting.
Here's a diagram of the "full banana" with Ground lights. Click on the schematic to expand to full size.
