I want to update this post. I found out that my Skyliner does have a GEN light. I believe it has a Motorcraft 3G alternator. Doing some research I now believe that these alternators used in original equipment configurations used a 500 ohm resistor in parallel with the bulb. This ignition feed through the bulb initially energizes the alternator upon startup. Without the resistor, when the bulb burns out, the alternator will not function. This could be very nasty on a trip away from home. Therefore I am planning to add the resistor.