I have a 2000 Prado 3L diesel with factory standard suspension. The vehicle has had the rear folding seats removed and sliding drawers fitted. The rear suspension seems to have drooped and I would like to raise it (vehicle second hand). When going off road the vehicle has a rooftop tent and fairly heavy load in the rear with provision/spares etc.It's also equipped with a long range fuel tank. I would like to fit OME springs/shocks back and front. Could anyone advise which spring rating to select?