Two New Old Stock, General Motors Part #3656690, Rear Spring Shackles, in the Original GM boxes, are for:

1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 and 1st series 1955 Chevrolet 3/4 and 1 Ton Trucks.

(except 1954 and 1955 Panel Van)

I believe it also fits all or most of the same year GMC 3/4 and 1Ton Trucks.