Peter will be quite familiar with these, but I must laugh at the 79 Series trucks set up for touring with thousands of dollars spent on suspension, yet they carry a wheel over the smallest wombat hole.
I realise that some 70 series are coil sprung and IMO, that makes it even worse. Spend the money to get an awesome suspension and it will pay dividends in many ways. I also find it strange that no one seems to use stacked transfer cases or ultra-low gearing in t-cases there. I must have watched a hundred hours of very well built Patrols and 70 Series touring or "over landing" just bouncing and banging all over the place because they could not go slow enough for the terrain they were crossing.
Couple this with a poor or mediocre suspension and you risk damaging your truck, the trail and having a white knuckle ride along the way, none of which are necessary.
A popular Toyota HiLux or mini truck upgrade is called RUF/63. This translates to Rears Up Front (OEM rear springs go to the front of the truck, nothing else changes), then a 63" Chevy spring is installed on the rear axle. The ride and flex, with some decent shocks, is drastically improved over the factory setup. Proper articulation allows your tires to stay on the ground, improves control and reduces stress on you and the truck. Flex is not for show or for "rock crawlers", it is the smart way to go off roading, IMO.
Getting proper springs ordered and dampers dialed is a bit of an art, so I am not sure there is a kit or a system that will be the perfect plug and play for your rig. It may seem silly to spend so much time getting components dialed in, but once you have ridden in or driven a rig that performs spectacularly off road, your mind will be changed.