I have not been in the audio harness in awhile but have swapped around many factory stereo units. The wiring will change with different generations, not much but it is not guaranteed that later or earlier unit will function 100% without repining a wire or two.
That loose wire with the insulated terminal is not to be in a gang connector. Without checking the books that might be the wire that commands the antenna operation.
The service manuals will have all the pinouts and diagrams for each radio should be available still with searching their PN.

Cheers, Charlie
If It ain't broke, Modify it!
87 Montero turbo Converted back in Spring1989
95 Montero SR 3.8 DOHC Only one?
93 Pajero 3 door 6G75 Mivec with paddle shifted 5 speed
Then a Gen2 SR with full coil independent suspension.