Electrical
For accessories with 100W or similar current draw, use 20A wire.
Aux Lights
The over ride switch is not essential, as most of the time there is no one around when you use high beam anyway. This also means you don't have to find a place for the switch and cut up to dash. If your factory lights are poor you will always be using the extra lights anyway.
Air Horns can be wired in a similar way, but not to the high beam wire!
Electric Cooling Fans.
Try wiring them with a little light in parallel with the fan. If the fan stops getting power, the light on the dash goes out and you know not to stop for red lights.
I have noticed, that if I turn the fan off at high speed, I get a little voltage going to the light due to the windmill effect. At 100km/h, a pair of electric fans can deliver almost 7 amps of current back into the charging system!
Finaly, here's a site that might be of use for those looking to improve or modify their starting and electrical system
Any problems?, bertrand@omen.net.au.