bear in mind 3 rear passengers ads up to about 1/4 ton so add that to your payload weight. I ran a trip called the gambian school run last year using two H60s. We were carrying around 3/4 ton school books between the two vehicles, 2 crew members to each, plus personal kit, spares and at out heaviest 60 ltrs of fuel in jerries and 80 ltrs water to each vehicle. I have no idea what the payload was, I didn't dare find out but nothing else would have physically fittted in the vehicles, and the fuel was on the roof.
The biggest problem we had wasn't the vehicles giving up under the strain, hit a rock in an H60 and you are more likely to shift the earths orbit than break it. The main problem was simply getting bogged because of the weight, even running with the tyres at 15 PSI.
MY own experience mirrored that above, I had two massive blowouts on XS tyres of indeterminant age and history on the Nouadhibou Nouakchott rd ('scuse my spelling there!) and we had a load of other less impressive punctures.
we were under time presure as well so were 'making progress' a bit more than is desirable but still didn't break anything on the suspension.
The long high speed haul through europe on the way back did break my gearbox though!! it would appear these boxes overheat quite badly if you are pressing on, you can feel the base of the stick getting hot.
1990 Landcruiser H60. Full rebuild completed 2014
2012 Hilux, mountain top and bedrug with GG AT2s