OK, I felt like torturing myself today; so I waded through my AMC parts books, and think I have a somewhat definitive answer re Eagle key changes. 1985 was the change year, that was when they went with the slightly different ignition lock & key (the RA-5 key with the little notch on the bottom). So here's the poop:
'80 - '84 All side doors in all models took the square-head key (RA-4 blank). The wagon, S/X4, and Kammy also used the square-head key in the liftgate / tailgate (RA-4 blank). The sedan however was different, and used the round-head key in the trunk lock (RA-3 blank). All glove boxes and storage compartment locks were the round-head key (RA-3).
'85 - '88 All keys in all models, except the ignition, were the round-head keys (RA-3). The ignition locks were the new RA-5 square-head key.
Hope this helps.