Richard being Chuck is what I first thought when I saw the episode, but then Charlie said Chuck returned the truck and Billy dropped charges, which we know didn't happen. Something more is going on here. There's another theory that Chuck = Mr C. and Billy = Dale and the stealing of the truck is a metaphor for Mr. C stealing Dale's identity, but who knows. It could just mean Richard after all. Then again in Eraserhead (Lynch movie) the father and the sun morph into one in the same, the deformed baby head takes over the body of the father.
Also, apparently Sabrina Sutherland (TP Producer) confirmed at one of the Twin Peaks events that the 'Billy' that Audrey mentioned is the same Billy the random guy came in asking for running to the double R at the end of episode 7 while the song 'Sleep Walk' played in the background.