the gauge will probably come with a sender using a 1/8NPT thread (looks a bit like an M8, ish)
you will need an adaptor to fit this into your block.
Use the spare blanking plug above No.3 piston, which is just in front of the turbo
i.e you get another blanking plug that has a hole in the top tapped to 1/8npt for your sender.
found one here.....
http://www.scoobyparts.com/acatalog/LMA_.html
If your sender is too big too get in the gap above, then you will have to fit
http://www.scoobyparts.com/acatalog/LMA ... PIECE.html
although the above talks BSPT, whereas most gauges seem to be NPT.
It may be an american/UK thing which re actually the same.