Jello Geoff
The best place to tap into if you have it ! There is a block about 5cm with vos fitting in between the engine and the gearbox its fan shaped I'll try and get a photo for you.
The other thing is if you have ar trailer brakes to come of the tank and last resort you will have a four circuit protection valve you need to come of the last circuit on that.
For some reason I cannot upload pictures due to my iPad !
Moose