".........I need to smooth some small dings on my running boards before I can get them powdercoated and plastic filler won't survive the process......."

I went by my friends Powder Coat shop a couple of weeks ago to see how he was doing. He showed ne some of the filler he uses that is compatable with the process, and some parts he had done using the stuff (I was impressed).

I would sugest that you go by the place your planning on doing the coating and see what they recommend.