Dual battery placement

[louie the fly]

I want to install a 2nd battery in my 92 4Runner but WHERE!!! Someone suggested behind the back seat but I'm not real keen on that idea.

It is a 2.8D with a snorkle fitted. There's not a lot of room. Can I move sumthin? BTW, it's right hand drive (Australia) for you guys who drive on the wrong side of the car.

Thanks.