Reason for the overflow pipe is merely damage limitation.
In your tin top if the rad cap blows it will cover everything under the bonnet with water and antifreeze. On the Dax setup it will hopefully drain the water away to the ground and not leave your lovely engine bay in need of some serious cleaning.
Wiring is not a problem. I have the latest diagram and colour codes so should be able to sort things out. There is another chap on here called Dave Brookes. He builds Dax's for a living so what he dosen't know about them is not worth knowing.
Craig.