I certainly think you made the right choice, if you wanted to get very technical, you could leave some bare and most cream, painting the ones with the right part number, as you discovered the part number difference yourself.
Honestly though, I would go cream to, even if it was a recall, and not on the initial production line, it was early, very early, I would say within 2 or 3 years, so close to the start, but to be honest, overflow seems also likely, as does experiment.
We can look through recall notices from the era, i know how to find them now, it's just a matter of waiting for them to cone up, as a recall of that magnitude would be documented, there might even br documentation if it was an experiment, there is for the late 60's carby experiments, but in general, untill evidence is found, yes, we rely on observation.
