Thank you for the input. It hadn't occurred to me, but I'm going to try to inject some silicone or gutter cement or something inside that spacer. I tightened up that headlight bezel, and that rattley sound has gone away. Such a thrill when I manage to fix something. I put in about 25 miles.
About halfway out, I was sensing some jerky motion. What now? It went on for a while. Seemed like the engine wasn't getting fuel on every intake stroke. So, I pulled off the highway into a parking lot, and the engine died. Looked at the fuel line, and it looked slightly more transparent than normal. Switched to RES, and watched the fuel flow down into the line. Made it to a gas station a couple miles away.
If it's not one thing, it's something else. Several years ago, i had to replace (twice) what I refer to as the sending unit (the grey thing on the front axle that spins the speedometer cable). My speedometer has never had smooth operation. Today, it was bouncing around more than normal, or it was indicating a speed that I knew was less than what I was doing. At another time, it was indicating a speed that I knew was more than I was doing. I know the cable needs to be lubricated from time to time. A project for tomorrow. It's pouring right now.