20 thread count 

7/8 inch socket 

measure before bid

threads into a 1967 Buick 400 oil pan but may fit others like 

Differential Drain Plug for

1957 150, 210, BelAir, Sedan Delivery, Station Wagon
1958 Impala, Biscayne, Bel Air
1958-1964 Station Wagon Impala, Biscayne, Bel Air
1959 1960 El Camino
1957-1961 Nomad
1962 1963 Chevy II Nova
1957-1967 GMC/CHEVY Truck 1/2 Ton
1957-1962 Corvette

Chevrolet car Engine Oil Pan Plug
1929-1967 6-Cylinder
1955-1967 V-8
1980 1981 Impala, Caprice V-8 350N
1989 1990 Caprice V-8 307Y

Chevrolet trucks
1938-1967 6 Cylinder
1955-1967 V-8

Corvette
1953-1955 6-Cylinder
1955-1967 V-8
1968-1982 V-8

Pontiac 
1935-1967 V-8

Oldsmobile
1955-1974 V-8
1975 Engine 260, 350, 455