Old Thread, but replying as I've recently done exactly this to my 2012 GT86.
As with many things ZN8 to ZN6, the steering wheel fits perfectly & is a great upgrade. Only thing to be mindful of is the airbag as mentioned above, though if buying a GR86 wheel from the same region as your ZN6 was originally from, you'll be fine. The connectors from the 2012 clock spring are compatible with the new GR86 airbag, plug n play. No SRS lights or explosions
If connecting a single stage airbag to a dual stage clock spring, you plug the airbag to the yellow connector (Stage 1/ Primary deployment) and a 2.2 ohm resistor to the black connector (Second stage deployment) to keep the airbag functional & avoid SRS lights.
*Please do more of your own research and at your own risk if adapting as per above - my GT86 airbag was single stage, so was the GR86 wheel I got, the above is only my basic understanding if it may help anyone*
Cruise control stalk is also working perfectly, though you do need to swap over the harness from the old cruise control stalk, to plug into the new one (30 second job)