[curtis73]

I might try a less expensive thing first. Most parts stores have spring "helpers" Some are rubber, some are cast iron, but they fit in between the coils. They usually don't change ride height, but since they remove one active coil, the spring's rate increases. This might be all you need. It worked on an old Caprice my friend had. The floppy sagging springs let it bottom out all the time, so he used a set of the rubber ones and it worked like a charm.