if 1971 gtx has factory drum brakes what size would they be 11+2 3/4 front 11+2 2 1/2 rear ?

11x3 fronts and finned 11x2.5 rear

042 3.23 open, 8 3/4, 10" rear drum - front disc/LD drum
043 3.23 S/G, 8 3/4, 10" rear drum - front disc/LD drum
044 3.23 open, 8 3/4, 11" rear & front drums
045 3.23 S/G, 8 3/4, 11" rear & front drums
046 3.55 S/G, 8 3/4, 11" rear & front drums, (A36 Pkg)
047 3.55 S/G, 8 3/4, 10" rear drum - front disc, (A36 Pkg)
048 3.91 S/G, 8 3/4, 11" rear & front drums, (A31 Pkg)
049 3.91 S/G, 8 3/4, 10" rear drum - front disc, (A31 Pkg)
050 3.45 S/G, DANA 60, 11" rear & front drums, (A33 Pkg)
051 3.54 S/G, DANA 60, 10" rear drum - front disc, (A33 Pkg)
052 4.10 S/G, DANA 60, 10" rear drum - front disc, (A34 Pkg)