I had a White GT500 with Blue stripes and clay barred them with no ill effect. I wouldn't clay bar my car outside at all unless there was shade and zero wind.
Meh, I had bad luck with the 2.7 in the Fusion Sport, but I had it tuned, so can't really blame breaking a valve on the engine. I'd look for low mileage Explorers if possible, or ones that had recent valve train work. I thought chain tensioners, chains, etc.... were problematic on/about 100K...
The guy is a lunatic for doing this in traffic. I'd say we're all guilty of speeding, but I do my high speed runs in areas where if Darwin takes the wheel, I'm the only casualty.