I run an electric fan on my 261. It draws 14 amps. I have it running off a thermostatic relay, wired directly to the ignition switch. I don't see the need for another relay, most of the current is drawn when the fan starts, which is provided by the thermostat. I have been running it that way for 2 years and haven't noticed any problem with the ignition switch.
Your generator is probably a 30 amp unit, which means that after running the fan (15 amps), the headlights (10 amps for 2 60W bulbs),and the ignition (5 amps), you have nothing left for the heater fan or the radio or charging the battery. If you are going to an electric fan you will want at least a 63 amp alternator.
