'62-'63 are most similar; cowl/dash/windshield area changed for the '64s, front upper door/vent glass frames changed too.
Firewall area (under upper cowl panel) looks very similar between my '63 & my '64, aprons, floors & some structural members are probably interchangeable. Lots of 1-year-only things on the '62s IIRC, mainly window mechanisms, rear doors, exterior sheetmetal. '62 - '63 dashes pretty much interchange, though the clusters are year-specific.
Some day I hope to have a nice '62 Savoy 2-door, always liked them.