Japanese domestic market S30-series Zs had a steering wheel with less 'dish' than Export versions, to accommodate drivers of a shorter average height.
Seat belt mounting points were the same for Domestic and Export markets until the inertia reel 'pockets' were added for the North American market. The only exception was the Fairlady Z432-R, which had extra shoulder harness mount points for the driver (factory 4-point belts).
The 'seat belt mounting points' mentioned might be being confused with the extra seat mount brackets of the Japanese domestic market models? These allowed the seat rails to be unbolted and moved forward into another mounting position, again to accommodate drivers of shorter average height. You might notice that the rear seat mounts on all cars had two sets of holes, but Export market models only had one set of forward mounting points. The two-position rear mounts on Export cars are an artefact of the Japanese market spec.
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