Several years ago, someone posted information on a 1954 truck in South Africa that had all 1954 parts/interior, except for a real split windshield.
Tim, I'm not familiar with S.A. Chevys production differences,but I do know that VWs built in S.A. had some real oddball mixtures of crossover parts.
So your theory of a South African built Chevy might well fit,although I imagine it
should be right hand drive?
Like you say the I.D. plate should clarify this.