Yes--they're pretty easy to lift. You can gain a little lift in front by cranking the torsion bars a little tighter. You can also use lift spindles.
In the rear, you can use leaf packs with more arch (you can't use lift blocks since you're spring-under) or longer spring shackles. You could potentially do a spring-over conversion. That ends up being quite a bit of work though.
You can also purchase long-travel complete kits for Pre-runner use from fabricators such as Total Chaos.
http://chaosfab.com/