These are the studs in the manifold for the header pipe. They measure 3/8 inch x 2 inch w/ 5/16 inch long brass hex nuts. For 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 Chevrolet Cars and Trucks