If it's one of those Mastercrap electric impacts, yeah you're pretty much screwed for the LCA bolts. I've got a Milwaukee electric impact that has yet to meet a bolt it can't break loose. Expensive as all hell and worth every penny

Anyway, back to more relevant stuff.. I would suggest popping the upper ball joint out. Loosen the nut but don't remove it all the way, then smack the SIDE of the knuckle where the ball joint bolts through. The knuckle should drop a bit (but stay held on by the nut), allowing you to remove it at your leisure