I think its about the RN25 thats runs a similar sized track to a KE3x/55. But the later model diffs are stronger. From memory look at the 4wd diffs, their stronger then the 2wd versions and plus you'll have the option of being able to walk into a 4wd shop and have the pick of diff ratios, spools (or lockers), LSDs etc etc
And if thats not strong enough then Dana60