Hey dd.. it could also be a difference between where they were made, and what the local assembler thought deisgnated one grade over another.
I mean, I know the GL looked much different in Japan, with all of the "eye sore" badge work of 1972/73, but I think you'll find the 3 models are STD, GL, DX.
GL standing for "General Luxuries" and DX for "Deluxe".

Also, I bought a book called "Datsuns of the 70s". It's filled with car magazine reviews from the UK.

And interesting quote from AUTOCAR Magazine 23 July 1970, for the 1200:
Quote:

I thought it was just that all the 1200s I've driven had worn out steering!