1972 and earlier are 1/2. The later 73 up cars have 5/8 eye. The holes are in a different location on the later cars. You can drill the 1/2 inch style but note they are in a different location. If you need some pictures I get some. Also the rear shackles are different sizes on some springs bought and take b-e-body bushings which may take modified hangers. Removal of the sleeve and a new sleeve installed.