I would replace the coils rather than using helper springs, simply because they are so easy to install and carry the load between the frame and control arms as in the original design.

Before purchasing any replacement springs it might be prudent to ask the size of the spring wire and compare it to the size of your originals. Most of the stock replacement rear coils I’ve seen are made of wire that is far too heavy and the springs are severely stiff. In theory the variable rate springs should be preferable, but I installed a pair of new aftermarket variable rate coils and the wire was so thick they basically couldn't be compressed no matter how much weight was added in the bed. The truck rode like it had no springs at all. As a person with back problems the truck became too painful to drive. I had to toss out the new springs and go back to the old originals.

1960 GMC 1/2-Ton Pickup Truck
In the Gallery
Updates in the DITY Gallery
Now cruising in the Passing Lane