I know this is on the fuel tank side but wouldnt be hard to move it across. Mine was very simple to make, just used 25x25 angle cut to the size of my battery (plus a little extra) and some flat steel as side braces. I also made plates that go inside the vehicle to help brace the wall as its only thin steel

http://datsun1200.com/uploads/newbb/5996_5135c4e21fd63.jpg

Have a look at my build, there are a few more pics of the battery tray.