Fitted a Shocklink to the Nav, I wasn't too sure about Nissans allowable coupling weights/dimensions, so thought I'd share what I learned on the way.

As of April 2006
Navara D40 details.

Max permissible vertical load on the coupling device for Europe, except Germany,Portugal and UK
2wd king & Dbl cab 80kg
4wd king & dbl cab 120kg

Germany
2wd king cab 72kg
2wd Dbl cab 68kg
4wd king cab 108kg
4wd dbl cab 104kg

Portugal
4wd king & dbl cab 92kg

UK
4wd king Cab 108kg
4wd Double Cab 104kg

Rear overhang King Cab & Dbl Cab
(axle centre to end of towball)
Step bumper 1334mm
Tube Bumper 1180.5

If anyone has any details for further models/years, please add to the thread.