Oh, never fear! I’ll get this figured out! But at this point I’m 100% confident with a 25% assurance that this is the problem.

But the good news is that in fact, yes, I do have the key-in-buzzer feature. Why? Because all 70s did! Frankly, I’m a 68-69 guy and that wasn’t standard on B-Bodys during those years. This being my first 70 and an E-Body to boot the learning curve is steep. So Darrell still gets some props for a correct guess.
And I did get that fixed along with the other electrical issues I thought I was having, so now the dying cat sound when the door is open and key is in waifs through the cabin much like it does in the alley behind an Italian restaurant in New York City.
It’s aftermarket, but no fluctuation of voltage between any key positions, Steve-O. There’s a short somewhere internally in that main harness. Gotta be!!
Cheers

Dave