They look like 74 and up Camaro door panels
The 3 holes for the arm rest mount
there are numbers on the inside but they not dates, oh well if they not mopar.
all are different, 50 429, 50 711, 50 621
i just compared them to some spare doors i have they are about a foot shorter than the doors. also they have metal uppers attached to the masonite, kind of like ranidart70 described