You'll need 14 or 12 gauge wire, 10 gauge wire, and a 40 AMP relay.
Install 12v hot to the switch (14 gauge wire should be fine), then that 12 volt switched (from the switch) to the relay (again, 14 gauge on relay terminal 85 or 86).
Have the battery hooked up directly to the relay (with 10 gauge on relay terminal 87), and connect the relay output to the fan (again, with 10 gauge on relay terminal 30).
Then ground the fan and the relay (ground the relay with 14 or 12 gauge wire on terminal 85 or 86, and ground the fan with 10 gauge wire directly to the negative battery post). This way, you can switch on the fan even when the car is off. (relay terminal 87a is not used)
If you want the fan to turn off with your car regardless (just for a safety measure), hook up a 12v keyed source to the switch instead of the 12v hot.
I'm pretty sure that's right.
Someone correct me if I'm wrong.
I'll be install a mark VIII on my small block in about a week os so as well (whenever it comes to my door). I'll let you know how it goes.
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