Could possibly be the bushings. check 'em out. mine are also shot.
And I saw on some car restoration show, that if you throw on a layer of grease on hte left and right of the spring, in between the individual leaves, then wrap a couple layers of suct tape, drive it for 100 miles, let the grease work in there, pull the tape, and squeek should be gone.
I personally would do that....but I understand some folks have done it....not here, but elsewhere.