From the MP3, it sounded like it was a rhythmic clicking rather than a random rattling. Was the clicking noise possibly synched with wheel rotation rate? If so, it might be a loose / interfering wheel weight.

And if you do substitue SAE bolts (not that I'm recommending that), the originals are M10-1.5 x55mm, class 10.9. 3/8" is about 9.5 mm, so yes, close to M10. The SAE equivalent of (metric) Class 10.9 would be Grade 8. Class 10.9 bolts + nuts will be marked "10.9". Grade 8 will be marked with 6 marks between each vertex and the center of the bolt head.

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2001 X5 3.0i, 203k miles, AT, owned since 2014