[valiant67]

I don’t think these radios had anti-theft yet in the US.
The displays on these radios could fail. Used to easier to just find another in the junkyard. But if the display fails, the illumination backlights should still work (and vice-versa). I suppose a failure in the dimmer circuitry (headlight switch) could render all lights off.
There are three power requirements for the radio.
1) constant power, pin 1
2) switched power, pin 2
3) illumination, pin 3
4) there should also be a headlight in sense, pin 4
These are all in the gray connector.

 

[valiant67]

I believe the only PCI bus connector on these radios is for the optional steering wheel audio controls. It is a separate two wire connection and has no effect on the radio operation (other than if those external switches , if present on the steering wheel, will function to change volume or stations.

 

[valiant67]

The case is all that needs grounded. Either a ground strap with an eyelet is bolted to the radio, a ground wire clips to the radio, or a ground clips to an eyelet that bolts onto the radio.
In your case, either of the prongs pointing toward your red clip in the picture above can connect to ground (as you're already using one for ground) or you can have a ground connected to the bolt beside the black clip. Either way is fine for the ground.

 

[valiant67]

There used to be a company that sold a display fix kit years ago when these were newer and replacement radios were not cheap.
I don’t see any display repair services any more. This may be a find what you can in the junkyard. When I was upgrading to an AM/FM/CD/cassette I think it took three tries to get a good one from the junkyard (which let me return the bad one for the next one until I found the hood one). Once I found a good one, it never failed.