Since it's already painted, I would go with rivnuts as Phil suggested. Those are also available from McMaster Carr. And you don't have to buy a ton of them. Link
I used some on my daughter's Jetta a few years back and the kit I installed included a flat piece of aluminum that was used to crush them in place using a bolt and washer that was greased up. So McMaster's $30 manual installation tool wasn't needed.

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.