These are Hooker headers I'm assuming? The 6210 and 6211 have minor differences in the drivers side tube if I remember correctly, mainly due to some of the later cars having a column shift. Drivers side is the difference. Ford Powertrain Applications offers a 66-73 4 tube for a 4v/2v that's kindof a universal fit, some clutch linkages may need some modifying. Check Network 54 or Google 335 Series Cleveland Forums, usually you can scrounge a set....