You are probably thinking of the TV series How the West Was Won, which starred James Arness as Zeb Macahan and Bruce Boxleitner as Luke Macahan.One other non-Trek guest who was interesting was Bruce Boxleitner. Obviously there were a lot of Babylon 5 question. He was a big supporter of the show and sorry to see it end (and kind of bummed that they had a spin-off without him). He was kind of jokingly miffed that Firefly got a theatrical movie and B5 didn't. He was also kind of a connoisseur of TV and movie Westerns (I think he was on "Gunsmoke" in the later years). He sort of blamed Johnny Depp and the ill-fated "Lone Ranger" for killing the genre (which I think is an exaggeration).
I just now found some of it on Youtube, which is terrific because I didn't get to see all the episodes back when it was first on (had a 10 pm bedtime back then, strictly enforced).