If you sling your axle under the springs and you have a straight axle it will raise you around 80-100mm, if your axle is offset you can adjust it with packers and have a smaller gain. The problem being with a car raising the van 80 -100mm you would have problems with your hitch levels not so much a problem with a 4x4.
If your looking for an extra 20mm, depending on your tyre and rim size you could go a larger tyre in the same profile, eg: going from a 195 70 to a 225 70 gives you 20mm but you would need a 7JJ rim otherwise the tyre would have too much side wall flex.
If your looking for an extra 20mm, depending on your tyre and rim size you could go a larger tyre in the same profile, eg: going from a 195 70 to a 225 70 gives you 20mm but you would need a 7JJ rim otherwise the tyre would have too much side wall flex.