Well i too have an 85 supra.
The one black wire should go to the bottom of the distributor,
I was just out looking at my supra and thats where the one black wire goes on mine, if you need further assistance feel free to shoot me an e mail at
js31085@gmail.com or message me on yahoo messenger
statick_xus@yahoo.com is my messenger sn.
good luck with the car
