Zenki means first, kouki means last, chuki is middle...
1986.5-1988 = Zenki
1989/1990 = Chuki
1991/1992 = Kouki
JDM 1989-1992 tails are darker and all 3 pieces match, USDM tails are two different shades of red and are lighter...
Euro Supras only got the zenki taillights due to the long license plates, but received pretty much every other update and some things we never got (rear fogs, headlight levels, etc)