In this "official" 1st episode, Hugh Beaumont took over permanently the role of Ward Cleaver over Max Showalter who had played Ward on the pilot episode. And Tony Dow took over permanently the role of Wally Cleaver over Paul Sullivan who also played Wally in the original pilot.
And thank goodness that the show's producers decided to change the casting of Max Showalter and replace him with Hugh Beaumont. I couldn't think of any other actor other than Hugh to play Ward Cleaver. and I feel the same way Tony Dow replacing Paul Sullivan in the role of Wally Cleaver I can't imagine anyone else but Dow playing Wally.
it would have been interesting to keep Paul Sullivan and Max Showalter for other roles in the series but I guess it would have been weird since they appeared in the pilot as said main characters, I would have introduced them later on at the end of season 1 or maybe season two or three and add them around there for episodes around but I guess it just wasn't meant for them to be for them.
Barbara Billingsley, Hugh Beaumont, Tony Dow and Jerry Mathers became the fabulous unit that made the show such a hit. Together they had chemistry, together they had magic and forever cemented in our minds as the ideal family of the late 50s
Long Live the Cleavers!