On the TV show Rides, Rad Rods by Troy had a Challenger/Cuda powder coat primed on the underside of the floorpan and maybe the interior. It's been awhile so I can't remember for sure. Their claims were it is more durable and rust resistant than any paint on the market. I can't remember if it was topcoated though. So, powder coat priming is being done, but I don't know any more than that. Google Rad Rods by Troy, or Troy Trapanier in Manteno IL. Look for the mopar built for Joe Rogin of Fear Factor, there might be some more info there.
John