New Springs
I finally bit the bullet and replaced the leaf springs.
The rear end on this truck has been sagging for a while, and I never found a satisfactory solution (add-a-leaf, air bags, etc.)
I ordered a set of springs and u-bolts from Michigan Truck Spring. I ordered u-bolts from them several years ago for the other truck and received really good customer service, so I gave them the repeat business.
The springs are OEM replacements, manufactured by a company in Pennsylvania. The springs are 4-leaf plus overload packs, rated at 1750 pounds. I upgraded to 5/8" u-bolts while I was at it. (The 5/8" u-bolts are grade 8, whereas the smaller sizes are grade 5.) I did have to open up the bolt holes in the spring plate a little, to fit the larger u-bolts.
The first picture shows the parts, the second picture shows the right side completed.