Maintaining 4WD after a V8 swap pretty much requires swapping a stronger solid axle into the front end. The stock LUV front end is very capable of being torn up by just the stock motor, and a V8 would easily twist parts into a pretzel. The rear is a bit stronger, but still not up to any kind of serious off highway use.
The V8 swap article here is entirely focused on 2WD trucks. Building a 4WD V8 LUV opens up a whole lot of other problems which would take an article twice as long to explain. I'd recommend looking over at
http://www.4x4wire.com at some of the info they have regarding axle swaps and engine swaps. Just so you know, putting in a solid front axle is commonly referred to as SAS, meaning Solid Axle Swap.
http://www.independent4x.com also has good info and products for the Isuzu 4x4 market, many of which can adapt easily to a LUV.