Most would be considered permanent. I've never removed the ones I have, so I don't know about the paint. They are high quality pieces though.
Edited to ad that these guys do static cling decals that are very non-permanent. I'm using their meatballs and numbers as well as a few others. They are also very good quality. http://www.cobracountry.com/opsplus/home.html
Cobra Make, Engine: Kirkham 289 FIA #690, FRPP 427 Boss engine
Posts: 764
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I had them on my coupe. Very good quality and should be considered permanent. I never tried to peel one off and I wouldn't want to! Here's a couple of pics:
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RCR GT40 SOLD to Fast 5
Kirkham #690 289 FIA