It is a common thing among the IFS Isuzu guys to drop the diff 1/2-1". (have a friend with a Rodeo)
However, there are problems to overcome:
First, I'm assuming that you've already found a way to extend your shocks our you wouldn't even be thinking abou this mod. Shocks are almost always the first to limit the travel.
1)the upper ball joint is the next to max out. this is a major issue. The Isuzu guys run ball joint spacers, but their ball joints are held on by 4 bolts, so they throw in a flat spacer and some longer bolts. Ours is the pinch bolt design, so you'd have to run a spacer similar to the trailmaster, which scares me. The other thing would be to run custom upper control arms, which could also help with aligning this 3" TT.
2)the inner tie rod max's out pretty soon after the upper ball joint. The isuzu is still a gear box rather than R&P design, so they don't have this problem. Even with the ball joints being my drop limiter I still wore out 2 sets of inner tie rods. I'm not sure what you could do about this one.
3) The Isuzu diff is held up by three bolts going straight up, so they just put some spacers in. Our mounts would reqiure either a) frame mods or b)droping the diff at least an inch to use the stock holes on both the diff and frame.
4) while you're no longer maxing out your CV's and then replacing them every 10k miles like i did. You are now adjusting geometry, so there is still a large possibility that your cvs will not last as long as you would like.
anyway, there's my 2 cents. . .don't know why I'm even bothering with you IFS guys anyway

j/k