door lock cylinders

I need door lock cylinders for my 68 Cuda, are they all the same or are A B and C different.Thanks

I'm pretty sure from about 65/66 when they went from the large outside chrome face locks to the small outside chrome face locks that they are all the same from then on (& the large/small face locks have different "keyslot" openings in the door. You can take off the rectangular chrome cover for the tumblers (not referring to the outside round chrome cover) & mix and match tumblers/spacers to get your key to fit (get em the same height (tumbler+spacer) to fit your key notches. be carefully with the lock tabs on the chrome rectangular tumbler cover as they are brittle when taking it off (move em just enough to get the cover off. Even if you only have several of the (5) passages functioning (if you dont have any spare cyls for parts to get all five the same height/functioning) no big deal cuz no one picks locks anymore (ex in the movies). EDIT the early ones have a peened rectangular tumbler cover & would need a locksmith to open it up or try drilling out a spare one & see how it goes