You can lift it a little bit by running extended shackles. You will only gain 1/2" of lift for every 1" longer the shackles are though. 2" extended shackles seem to be about the most that you can really run without problems with caster and pinion angle.
It is much better to lift the front with springs then with shackles though. If you need to gain a little extra lift 1/2" or so then longer shackles are ok. If you are going to try and get alot of lift from shackles you are looking in the wrong direction.
Harley