PAYLOAD capacities and dimensions vary between utility models, and for cab/chassis models depend on the manufacturer of the tray body.
Navara load space dimensions are not the same for 4x2 and 4x4 utility models as with some other manufacturers, so check the exact model you have in mind to be sure you have the load space you need.
ST-R 4x4 dual cab payload dimensions are: length - 1395mm width - 1390mm height - 435mm.
ST-R 4x4 dual-cab payload weights: tare - 1895kg GVM - 2920kg payload - 1025kg.
Towing capacity also differs across the range with the V6 engine down 1000kg on the diesel so, again, check the specifications of the model you are interested in carefully.
The ST-R 4x4 dual-cab ZD30's maximum towing capacity is 3000kg with trailer brakes and 750kg without.