I partially wired in my outback CC when doing a TT engine swap.
I aim to get the rest up and running (need to chase some signals in the CC switch and extend the actuator cable, use a WRX actuator with longer cable, or move the actuator closer to the throttle body).
The wiring for the factory cruise is pretty straightforward, so I reckon you could retrofit a gen3 CC without too many hassles. Just needs power, speed from existing gearbox sensor signal, wires through the firewall to the actuator and electric vac. pump thingy.
There was also a factory option cruise on older subies. Wiring for the factory Gen3 cruise is very similar.
I've attached the subaru factory option for '97 Impreza, and the foz cruise wiring diagram, which I found closest to my outback CC.
1997_Impreza_Cruise_add-on.pdf 616.71KB
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foz_cruize.pdf 39.08KB
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