Bummer that the Mustang never got the steering wheel buttons. I run an aftermarket stereo and there are adaptors available to convert from hardwired factory controls to a modern setup for steering wheel audio controls; IIRC, some Japense cars used similar setups in the '90's. The issue is getting a steering wheel and clockspring (and possibly column) that could be made to work for an SN95. You had my hopes up for a bit there, but oh well.
The two wire audio control setups generally use different resistances per button, same as the Ford cruise control buttons for older stuff, not sure when that started or ended, though. I know Pioneer decks have a hardwired control that works this via resistance between two wires, and other aftermarket decks likely do as - hardwired remotes were common for a while, and I've heard they are popular for boats so the deck stays hidden away and dry. Other makes of cars did something similar for early steering wheel audio controls, though not on the horn circuit like Ford did for the cruise control, that was...creative... and ended up not always working as well as desired. My '86 F250 used this setup for the cruise, and making it work is... fussy. As stuff ages, the resistances tend to creep out of spec, and it doesn't always want to work unless you mash the butons and hold them down. Before clocksprings it was better than nothing, but having dedicated wires per button, or a canbus connection to all of the buttons on on the wheel, is
so much better.
I've often pondered trying to retrofit a clocksping from a later model, or finding one that was "close enough" to work, but specs are hard to find, so it would be trial and error, and messing with the airbag gets dodgy real quick, as I don't want to disable the airbag if I can avoid it.
