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). It does seem as if the lower hinge aperture is wider, but still has the cut-out, but it is the A-post that narrows slightly from top to bottom giving that effect:

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: