Gday guys, I have to upgrade the battery in my EB 4.0L and was heading towards a deep cycle one due to my large stereo. I have upgraded all the + and - cables to 4 guage and my volt meter goes down to around the 12 mark and my headlights dim.
I'm just wondering what everyone is using and what is actually able to fit in the engine bay?

Batteries I am considering are the Exide Orbital, Optima D34 and Deka Intimidator but I'm not sure any of those will fit.

optima blue top - dunno what fits in the engine bay as mines in the boot, but i got a big delkor truck battery to fit at one stage by pannel beating that lip on the battery tray.