Relays

[Cool53]

A relay is used to make the shortest run possible for the circuit carrying the load, and to use a circuit that carries very little load to turn it on. So if you place your load wire in place from source to load, cut it somewhere and add the relay in the most convenient spot, then run the trigger wires then you've used the relay to it's best advantage. Putting all your relays in one spot then running load wires all over the place looks nice but defeats the purpose totally.
There are some really complex wiring/relay/electronics boards being sold out there right now. A friend of mine just bought them for his '57. You really need to look at that kind of logic to see if it is going to do what you need. Expensive and complex is not always the best way to go.

[62131]

I agree with you, really my thought is to keep it a simple as possible to keep cost down.

[Cool53]

And voltage drop at a minimum!

[ghost28]

I know electric fans pull a load and requires a good relay to work properly.

[cocobolo]

Guess I'll be facing this sooner or later.  So the best idea is to keep the relay close to your fan then?  (Or whatever it is you are powering.)