Since I first saw this thread I have been trying to think of who would have been an appropriate actor to cast as Sam Beckett back in 69.
I was completely stumped until I just had this idea -
I am partially basing this on the fact that he also starred in a pseudo-anthology drama The Incredible Hulk.
Bixby had a similar likable "Every Man" quality which kept viewers interested in mostly new characters and situations each week.
But also he would have been the perfect age in this period. While his role as David Banner was nearly a decade away in 1969 Bill Bixby was still only 36.
He was primarily know at that time for starring in a Sitcom. Which would have been approprate. While QL tended to be drama the role of Sam Beckett often required comedic reactions to the situations he found himself in.