Torsion diffs are really good and I'm sure you can fit them straight into a safari/patrol or most Toyotas. They work the opposite of a normal diff, giving all the drive to the wheel with the traction. A mate of mine in Wanaka has fitted a number to serious off road rigs down there, especially in the front for steering and traction and a few customers have even removed their diff lockers in the rear after having fitted them in the front so they could be worth looking into.
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