IIRC, the "demo" car had black interior.
Miami Vice used in-service cars and troopers when they filmed some scenes; can't say the same about CHP. That car sure looks/sounds like an in-service car, though.
As for the steering wheel, there's a bazillion in-service pictures that show what the cars came equipped with. Here's an article from Motor Trend in 1982 showing the correct wheel:
http://www.motortrend.com/features/a.../photo_03.html
The same wheel is also depicted in page 3 of the 1982 Mustang brochure.