Checking back in after I wedged in a keyring-sized shopper card into the gap between my driver's side strut tower and brace.
At first I thought it wasn't working, as I still had some clunking. My first attempt had the card pushed into the front of the gap, with the short end of the card pointing toward the front of the car. More than half of the short card was still visible. But at lunch I popped the hood and pushed the card a bit farther back and filled the driver's side edge of the gap toward the fender (the tightest part of the gap) and upon leaving, voila - no clunk.
Obviously a half day isn't enough, so I'll leave it there for tomorrow as well and report back again.
Zillon - thank you for taking us along on this clunky ride. I have high hopes for your replacement parts. If it works, I suspect quite a few of those parts will start flying off the shelves.