A "half-cut" is where you literally receive one half of a cut-in-half vehicle, so you'd get everything in that half like the driveline, suspension, hopefully the electronics and such. That's not too bad a price if it's already here and convenient to go get, at least the engine would have the mounts, harness, accessories and should be somewhat protected by the rest of the truck.

Piotr, that 3.0L is the dreaded 4JX1 which is absolutely the last diesel you want to be looking at. Ask any Australian Isuzu enthusiast about it and they'll either roll their eyes or admit to being some kind of weird masochistic diesel fetishist.

As for mileage with the 4JG2, it should be in the mid twenties. But remember, going diesel isn't necessarily about economy so much as it's about using a more environmentally friendly fuel you can brew at home, should you so desire. If you go with the 4JB1 you'll see less as you'll be working it to death in the VX. Go drive an '84 Diesel VW Rabbit and if you like that go with the 4JB1. The NPR motor is the 4BD2 and is quite popular with the light-truck crowd, but is just too heavy for the VX. You'll kill the handling and would have far too many suspension mods and clearance issues. One thing you have to remember is that all Isuzu diesels have industrial counterparts and Isuzu is very, very big on drawing from the common parts bin which translates to good parts interchange.

Another thing: How much of a diesel mechanic are you? If you aren't at least a fairly competent one now, you better have some extremely deep pockets. Diesel mechanics see dollars flying past at warp speed when someone wanders in with this kind of project.