You mean like this?
I elected to make my winch removable wich ment I needed to mount a 2" hitch receptacle to an 8mm Gusseted Plate which bolts to the chassis horns with bolts that go through the bull bar mounts into the horns. much like this
Note that these pics are of a Patrol and the Nav's bull bar mounts are different. They consist of vertical plates sort of like the Patrol but they also have substantial location plates that sit on top & bottom of the horns and your plate will have to sit on top of these and the bolts must also pass through them.
This is how Mine ended up looking.
Be aware that getting nuts into the chassis horns is the biggest issue in this. It involves cutting open the horns either on the front or the side in order to get the nuts in. The Navara Horns seem to be much more robust than the Patrol ones pictured as the ends are completely closed in with a separate plate and there is an internal plate/gusset inside the horns made from 2mm sheet that runs along the top but with a 5mm gap. I drilled straight through them and with Hi Tensile bolts just crushed the plate until the gap was closed up and left it at that. No other way to describe getting the nuts in and tight but as a complete pain in the arse.
Having said that I'm very happy with mine but I dont think I would do it again. I'm a fitter and pretty handy with tools but it took about 4 hours to make my plate and paint it. About 12 hours to fit because I'm fussy and wanted to get all the clearances nice where the hitch pokes through the bar. This meant the bar was put on and off about a dozen times and thing tweaked until I was happy with it.
My 8mm plate is 200mm wide and runs about 5 mm behind my bar exactly in line with the bottom return in the bar. I machined cut outs to clear the various hoses that are in the way andt he hitch was then tacked in place and 2 full width 60mm high gussets were welded on each side that taper to 30mm at the ends. The whole lot was them stitch welded.
DO NOT WELD THE PLATE TO THE HORNS!!!!