Squeak chasers, I need help!

Hi Guys. This thing is driving me crazy. I have a 231,000 mile 1974 Duster with all original stock suspension components. Every time I go over a bump, I get a loud squeak from my rear end (the car's, not mine). It seems to be coming from the leaf spring on the right side. Any ideas as to what causes this and how it could be eliminated? Pretty sure it's not coming from any exhaust components. All that stuff is new and in excellent shape.

Many thanks!