Hey All
Well dual battery is now installed. Very chuffed with myself! ARB dual battery kit installed is $700 including battery. I did it myself for $360
ARB Battery Tray $112
Deep Cycle Battery $100 (Thanks to Kazdan 69!)
Redarc Solenoid $110 (Ebay)
8DBS Starter Cable $50 from local electrician
Install time took me under 2 hours.
Here's how it turned out.
Thanks for everyones advice and knowledge. I might put up a how to do with pictures in tech section for anyone else wishing to do it. I have to say that it was pretty easy to do.
Chris