I have a set of Hellwig overload springs for sale. These were on my '65 C10 and before that they were on a 1967 C20 so I guess they fit trucks with coil rear springs. I think these are called quarter-eliptic. They consist of a beefy leaf spring that attaches to the frame behind the rear wheels and all the hardware and brackets to install them. I even have the original instructions. I probably cannot ship them as they are pretty heavy. I'm located in San Jose CA. thanks, Bruce