For all it's worth, the exact same thing happened to me in my 67 Mustang at night and I lost all power and could smell smoke and it happened right after I pressed the high beam foot switch which at least gave me somewhere to start looking. Turns out that when I was hitting the foot switch or had my foot near it, the carpet was pulling on the main
wiring harness that would cause it to rub against a very sharp metal piece on the steering column so it would cut through the harness and cause a short. I found it by following the harness with my hand and I happened to cut myself on the metal piece, pure luck but sometimes lucky is better than good I guess. Took 3 days to find!
Good luck.