Well, the active signal from the floppy drive and IDE hard disk is combined to make a single light on the Falcon. I think it's the Yamaha chip that makes the flicker light. You could put an LED in from the floppy drive, and another from the IDE hard disk. If you look at front of most floppy drives you find a space for the LED to solder. IIRC the ST drives had the LED, but plastic covered it up.
