Early 77's were located in the left fender. Late 77's were incorporated into the doorlock. I have an early 77 L82 and it's in the fender. This is the reason I had to do a little more work to find the correct dash harness as the two are different. Best of luck!

Hello,
I was at a Vette display at the Chevy dealer that sponsors my club. My factory alarm chose that day to come "back to life" when I locked my doors. I didn't even know the thing worked, but there I sat with the horn blowing and the starter disabled not knowing what to do because the key switch in the drivers door wasn't responding. Fortunately, one of the mechanics was still in the service dept. He told me to try the passenger door as that door was also wired to control the alarm.
It worked and the alarm shut off. I don't know what year they started wiring the passenger door lock, but it sure helped me out that day.
Take care,
Tom

In 78 the fender keyhole was removed and GM changed to the Clifford Security Alarm system activated by remote switch. We had to have it removed from Ian because it was shorting out the battery.Just to clear up the keyhole year question.