The whole datsun/nissan badging thing was dependant on the market the car was being sold in prior to the datsun name being dropped in most markets circa early 80's.
Like benny said, in australia they had the L24 vs the L20. A S20 GTR was availible in Japan only, think production numbers was 100 units in total.
Cosmetic besides badging was the tail lights, door mirrors to satisfy ADR requirements, GT model was also offered in aus early on not sure on the mechanical spec there.
My mates C110 when it had the Aus-market rear tails
And now with JDM rears
[F3ARED] 76 Isuzu Gemini Coupe - forged G180z, EFI, 525hp Turbo, 6years and still building...
Daily 78 Isuzu Gemini Sedan, stock G161z, Rodeo EFI, 500hp roller, 157rwkw. Fun