Many Twilight Zone afficionados consider Showdown with Rance McGrew to be one of the weaker episodes of the entire series and I concur with this assessment for the most part. Although the episode itself is not very good it's mostly a case of an interesting concept being ruined by poor casting. The script itself, which has the ghost of Western outlaw Jesse James haunting a no-talent actor over how James is being portrayed on the TV screen, is actually interesting and original. Unfortunately, a good idea got ruined by weak casting and the episode becomes a mess.
They should have cast a then current cowboy star as Rance McGrew. Either Jack Kelly from Maverick or Eric Fleming from Rawhide would have been great in the role. Almost anything would have been better than Larry Blyden, an untalented hack who eventually became a game show host because it was the only way he could get work in Hollywood. I didn't find Arch Johnson very believable in the role of Jesse James either. Johnson was a decent enough character actor from the 60's who was the wrong choice here. James Best should have been cast as Jesse James. He would have played the hell out of the role especially if he had been opposite someone like Fleming or Kelly.
Though it's always interesting to speculate about what might have been we're stuck with what we have on the screen. Showdown with Rance McGrew is a lesser entry in a great series. Skip it if you want to see what the Twilight Zone is really about.