I can't call it 86 (Hachiroku) with ease, knowing well that that is another car that I have worked with for 20 years...
For me, it will be FT86 or whatever the Japanese tuner market will call it as general referred model name.
ZN6 seems to be catching on, as that's pretty much how other cars have been named in the manufacturer side of things, by its chassis code in Japan.