I just picked up an 87 GT cheap and im putting BBK long tubes on it and I needed to know will i have to get a extension for the wire harness for the O2 sensors or will a 16.5" harness work?
i didnt use the extension... the wires are zip tied to the starter cable. cut the zip tie, connect everything, then re zip tie the harness to what ever you can. i used a solid power steering line that came right out of the rack.
I got some wiring harness extensions from Summit when I put mine it, I think they were BBK brand as well. I think they were only $20 or something. Worked perfectly.
No one can tell you if a 16.5" harness will work, every set-up is different so you can try and see. I personally also used the BBK extenders for $35. Not worth the hassle of soldering wires.