I LOVE older Isuzus. I forget what year they changed from the 3.2 to the 3.5 but if you still have the 3.2 do you have oil consumption issues? That was the one reason I stuck with older Isuzus (specifically G180, G200, and C220 powered guys). Post GM ownership Isuzu had some problems, but I still think chassis and axle wise they are better than Toyotas (and yes Ive owned both). The 8.6" rear axle your Trooper has is honestly a Japanese produced Ford 9", except better (if I remember right Isuzu actually copied the 9", just made the gear set a bit smaller, but its thicker so actually stronger). Only thing that lets them down is the 4L30E trans and the V6s (though the 4Zs werent much better)
Oh and to add, if the Isuzu V6 ever gives you any problems they really arent worth it to overhaul, a GM 60* V6 is a direct bolt in (3.1L and 3.4L)