A-body upper control arms

Can anybody tell me if there is a difference between upper control arms from a 1973 plymouth duster and upper arms from a 69-72 a-body. Both cars had disc brakes. I am putting them into a 1966 Valiant. I have a complete large bolt pattern disc set-up from a 73 duster but my upper control arms are rusty. I have a nice pair from an earlier a-body that had discs (69-72), they look the same. Are they interchangable? Any help would be great!! :thumbup: