Well my car is a different car with the credit card wedged in there. I took it for a spin tonight when it was 57 degrees and my car was sitting outside. I could hear the sound a bit but it was muffled and the rattle frequency was faster. Without the credit card shim it vibrated at about 32 cycles per second (in musical terms, 16th note tripletsat 60 beats per minute) and with the credit card it vibrates faster, about 50 cycles per second (16th triplets at 90 beats).
I wedged another pece of credit card about and inch and a half away from the bolt where there was more play. Took it for another spin and its silent. The whole car actually feels better. It feels great.
In my opinion Ford has never spent any time on this. If they did, they would have stumbled on this loose area long ago. Especially if they were using chassis ears.
I'm glad zillon is narrowing down and homing in on the solution. Thanks zillion:)