Engine quit, instrument panel stayed on, noise from driver's side fire wall

What the hell is it

I was backing my 66 out of the garage, and the engine stopped. I pulled the key out and the aftermarket tach and instrument panel lights stayed on. There was also a noise that appeared to be coming from the drivers side firewall. The noise happened every 3 seconds or so, and when it did, the dome lights dimmed. The noise is hard to describe, almost a hesitation noise. Not a hiss or anything. Obviously had to be electrical.

The tach and panel were "spayed" into the existing fuse box, so I pulled these out. Noise continued. I tried to start the car, it would turn over, but would not start. I unhooked the battery and put the car away (I was a little ticked off, so I let it sit for awhile).

Yesterday, I connected the battery (tach and panel were not connected), and the car started right up. I didn't have the noise, and everything seemed fine.

I'm thinking it is the ignition switch (I pulled out the tumbler, but can't get the bezel off. I am going to order the bezel tool soon). Could it have anything to do with the tach and panel being spayed into the fuse? Should I splice it into an existing wire?

Any thoughts? Thank you for your time.

Thank you for the replies -- and now I'm more concerned, which is a good thing. I wasn't going to worry much about it, but after reading the comments above, that is the wrong way to look at it. Time to do more investigative work.

Thanks!