Dean, sometimes I assume too much. this time I assumed you had the wiring diagram for your conversion.
Here it is:
Notice the resistor in the top blue box. Use a 1/2-watt, 560-ohm resistor. Any radio shop will have one. The resistor simply connects across the light bulb socket. You cannot stop a bulb from burning out so the resistor keeps your charging system going whether the bulb burns out or not. It also shunts a small amount of current which stops that flickering.
Hope this helps. - Dave