97 Tacoma with 280,000 miles. When loaded down high speed wobble occurs. Leaf Spring problem?

High speed wobble (60 and up) when loaded down. Shocks only 20,000 miles old, but had a broken shock for a 2,000 miles of driving as someone told me my leaf springs were broken. I discovered the broken shock, fixed it and took a close look at the leaf springs which looked fine so I figured I'd load up the truck and go camping. Wobble was difficult to deal with, but I'm not sure if the wobble is because of the old leaf springs or something else. Help?