At this point it might be a good idea to take it to a Chevy dealer or a reputable suspension shop and have them take it for a test drive then go thru everything. May be something simple which could cause damage in the long run if not fixed properly now.Spending a little $$$ now may save you from spending big $$$ in the long run.Good luck!
BTW....Dont know if this is even possible but can the V6 springs fit a V8? What PN were the springs? I have seen things mis-labeled before.