mine sits crooked too. passenger side and the back are lower.. i haven't messed with it much except to put on used (but better) stock springs..(thanks B.) that helped somewhat.. jgc/ford coils will be next and so will be doing the crank/re-indexing.. i am thinking that should do it...
now, for you that's probably what you might have to do after you take care of the other problems.. vibrations of the tires: low air, worn out tire, busted belt (in the tire,) out of ballance; ball joints, TREs, CL, IA, PA, stabilizers, and links, and a host of other ills are possible.. start at the top of my list and work your way down..
creecks: kind of keep your eye out for bad rubber (bushings) and anything loose or bent..