Modified 'check-stop' type on the left which have the additional components as indicated by the green arrows, original on the right: (Rimmer Bros)

Later A-posts have a cut-out on the inboard vertical of both upper and lower hinges, but this isn't where the additional parts of the modified hinges are. The following are crops from a single eBay image (left), and comparing the distance between the inner edge of the aperture for the top hinge (centre) with the bottom (right) the lower hinge aperture does appear to be wider (as one would expect for the modified hinge) but still has the cut-out:

73 CB hinges - plain apertures albeit with the inner vertical of the top one (left) a bit chewed:

75 V8 hinges - plain lower aperture (right) with a semi-circular cut-out in the upper, for some reason: