Hi hartster,
The gap on mine was just over the 140 mm. Mine fitted in the gap no problems. The gap that I measured is between the air box, and a hose coming out of the brake reservoir. There is a little bit of wiggle room in that 140 mm they say but I doubt that there would be 20 mm. I am not sure about the 2012, but in mine, 2014, there is about 50 mm extra under that hose I measured from to the end of the master cylinder. If you redrilled the bracket another 10 - 15 mm lower I would be able to use some of this space to fit the provent, but because the drain hose (from the provent) is very close to the guard, the provent would have to be put in on an angle to make this drain hose miss the guard. I am sure that the hoses supplied would be flexi enough to do this.
I hope that was clear enough to under stand. Here is a picture of where i was talking about.
Good luck, I live not far from western filters so i was able to go there and physically hold the parts in place to see if they would fit before i bought it. Being in WA it would be a bit of a commute for you to do that. I believe that WF in blacktown get these brackets made up specially for them, maybe there is someone over there who does the same, or maybe you can make up a bracket to fit it elsewhere in the engine bay and buy the generic kit (provent and lengths of hose to cut to suit)