This is all quite off topic now, but I'll give my insight seeing as I was asked.

I work in the auto industry, I have for the past 8 years, specifically in design. I do everything from concept to production for all parts of the world including Japan and the US and work on both interiors and exteriors.

I obviously wasn't in the design team that worked on the 1200, but I can take a pretty good guess as to how it went and I think you're pretty close in that the team were trying to replicate the US muscle style, but in a smaller way to work in their own country.

All design is borrowed from somewhere, whether that's from nature, or in the case of the majority of the auto industry, from other aspirational cars. When we're working on a job that is small and economical, we don't have pictures of other crappy small economical cars because they look #OOPS#e, we have pictures of things that we like and we try to work that into the job. In the case of Datsun in the 60's and 70's it just seems that the lending of ideas was rather literal, less interpretation, more copy.