I know that the Ford wagons of the early sixties came with a beefier rear leaf spring , along with 1/2 wider steel rims, compared to the full size Galaxy passenger car's . I don't know what year that Ford stated to do this, but dose any one know if the 1955 thur 1957 Chevrolet Wagons had a heaver rear leaf spring. Also there's a company called "Eaton Spring" which I have had good luck with on other car's . They were an original OEM supplier from back in the day, and are still making them today.