The '87-88 TC harness is a monster of integrated everything from what I've heard. No personal experience though.
Repinning the Mustang harness is pretty simple, so I don't see any reason not to. The only hiccup I see is that the '83 TC engine may have different connectors than the '87+ engines. It may be easier to use the '87 TC engine in that regard. Besides that, it's intercooled and rated about 40hp higher than the '83. Adapt the '83 Bird's T3 turbo or get an SVO compressor housing and it will be muy bueno.
Thanks. This got derailed because the 87 engine seems locked up, so I has to come out and be gone through before trying all this. Also discovered I have a spare 89 Mustang harness in a box in the garage. May move another project ahead of it. Probably the door swap on the 89 and the head swap on the 82.