Hi Terry,
Inside the frame there should be a a shim about 3/4" long welded inside the frame to center the spring, is it still there? I used a stainless bolt to avoid the bolt rusting causing squeaking. Were the spring bushings replaced. I have seen the wrong bushings put in, if they are to small they will squeak. the rubber leaf spring pads if not correct or put in can also cause a squeak.
Hope this helps
Lee