Door locks, trunk locks, ignition lock cylinders....

I found that it was '65-6 that was the major change in trunk locks. They went from a flat sided key in '65 to a groove key in '66. The lock cylinder changed in other ways too from an enclosed pin chamber that required you to remove the outer bezel to re-key, to one where it was a simple cover to re-pin starting in '66. IIRC '67-'68 was the change in how the tail shaft attached to the back, from a fork style to an eye style shaft.