Appears from the parts book that it is for a 66 Belvedere. Coronet is 2533504/5. I probably have a decent set of 67 Coronet bumper brackets. I can check if 67 is the same. PM me if interested.

67 Coronet 500 9.610 @ 139.20 mph
67 Coronet 500 (street car) 14.82 @ 94 mph
69 GTX (clone) - build in progress......