Mepr has it pretty much covered unless you get real creative with a welder. You can expect around 3 inches from cranking the torsion bars in the front. In the rear you can go with extended shackles (make em yourself or they can be bought quite a few places) or you can change/add springs. You could rework the rear spring mounting to put the springs onto the top of the axle (aka SOA or Spring Over Axle), but that would give you about 6 inches which you could not match in the front. Combine SOA with removing some spring leaves and you might find a good balance.
If you want a source for general info and parts for Isuzu suspension lifting check out
http://www.independent4x.com and look at their FAQ and lift parts sections. They don't focus on LUVs so much, but I'm sure there are some parts that would help. I got poly spring bushings there for my 86 Isuzu Trooper and they also fit my LUV. If you want to really lift the front, you can also browse the front axle section for SAS (Solid Axle Swap) info.