yellow plug in left pic looks like 2.3L fan controller plug.
Box in the right pic is the 87-89 low fluid modules that activates the little 4-light pod on the bottom right corner on 87-89 GT's. Looks like it's been smashed out it's protective box cover.
The low fluid module is what I thought it was.. After tracing a couple of wires to it that were not being used I popped open the box to see what was in there. Pretty sure they went to the black square plug in the pic. So that means that can go away!
Still not sure on the other 2, Did the 2.3 and 5.0 run the same harness maybe. I am pretty sure these were not plugged into anything when the car was running. Just trying to not hack away at everything Starting and running I can make happen, just want AC. lights. and wipers to work too.
Yes, the 2.3L and 5.0 along with coupe/convertibles all ran the same dash harness year for year. So there are a lot of unused plugs in there for 2.3L stuff, or things like convertible top relays or the defrost relay (if equipped).