Seat brackets look to be 1965 SS, so seats could be also than?
Or A-100 Pic-up (folding).
Possibly was 4 brackets of the same size used, since left and right bracket ( ยด65 SS B-body ) is very different in height.
Seat brackets may be. The seats, not sure what they are from but they were painted black from their original color. I am going to have them redone with the same pattern.