Mongol.
General Grabber At2's come in an alternative 305/50R20 which are just over 1" taller than stock Rangey Sport tyres with rims.
The current DickCepek's need a 9.5" wide rim to sit on, where as the General Grabber only requires an 8.5" wide rim to bolt up to !
If the truck is running off-highway nearly all the time, the General tire is Xtra Load rated which should support your truck with say full load of fuel and five adults on board and a minimum air pressure of 23psi would be necessary for very smooth travel ?
As long as you're not driving on tarmac at ultra high speed, the At2's are OK because the General's are speed rated T[140km/h].
From the obvious destruction of your Conti' rubber the first and second outing, the Off-road conditions sound pretty hard work on the truck, reminds me of the 7 hour trek including 28 river crossings I made earlier in February 2009 just to visit my mum in the Solomon Islands. My uncle managed to bust one of the front shocks in his new 79 Series Toyota Land Cruiser 4WD ute on that trip, So if this is the sort of extreme terrain your truck will experience, it may need more than better tyres to survive.
Cheerio,
Vinniman
'88 Highline
Perth, W.A.