Ideally buy a multi-meter and test for yourself...
Just to understand what you are trying to do (electrics are my strong point)
Where do you intend to run the main power to the fan from as the current draw to a fan is significantly greater than a washer pump (3 – 4 times) and as such the wiring infrastructure needs to be more significant.
Ian, I would run your electric fan via a relay. Find a 12v ign source to power up the relay and then run a new fused wire from the battery which powers the fan via the relay. If your doing an RB swap in the future, I would consider making a sub loom with relays and new wire to power your ecu, and fuel pump as well. Running any of that stuff through the old datsun wiring and ignition switch should be avoided.
I can't remember the exact circuits but I know the fan was into an ancillary cct so that I could let it run after a track session without the ign on.