I actually tried to find that guest appearance this morning! Unfortunately, I don't see it available on Netflix at all and I'm not sure where to look. According to IMDB.com, he had two other guest spots on Gunsmoke, both of which are available. One of them also has Simon Oakland!

I haven't seen Riverboat either, but I've certainly been thinking of getting the DVDs Netflix has for it. And that is a gorgeous picture. Yes.