Twin batteries

Going to fit twin batteries to me Disco 300Tdi.
So do I need to move the air intake?
Best place to connect the cables?
I was thinking one to the starter motor live and the earth to an alternator mounting bolt as its nearby?

Pull out chock and jack under bonnet, prise out air intake elbow to wing, put battery in the space. Wire up using a split charge system either diy or bought. I recently made on and posted it on here do a search. Works well. I used an optima red and blue top but in reality any decent batteries will do.

Thanks
Wasn't going to bother with split charge as I only have a few extra electrical bits so happy with two batteries connected together

If doing that at least use 2 identical new batteries. Wire pos via cable from batt to batt then earth 2nd battery to somewhere decent near as possible. Use thick cable and decent connections, keep cables short as possible.

Why would I have to have identical batteries?
Had a good look at it and the original battery hole is too small for the 800CCA battery I have so I will have to trim 10mm off the radiator mount, the air intake side looks ok just make a bracket to move the power steering reservoir out of the way.
Should be able to get to the scrappy tomorrow for some more cable

You dont have to, its just recommended. If you fit one battery that sits at 12.6v for example then one that sits at more or less v, then they will both equalise to same volts ie one discharges one charges. Not seen as being good for your batteries and will shorten their life. The bad battery will drag down the good just like a bad cell on one battery drags the whole battery down. Split charge is the correct way to go but what you suggest is not dangerous or anything, just very basic.

Thanks lets see how I get on

the way you have said is how i had my last 300tdi wired up and my 200tdi the only problem i had on my 300tdi was that the lights slightly flashed like they had a heart beat if that makes sense when its was running but other than that its was fine it did not do this on my 200tdi though