Had to be there -- every Saturday morning! First a T-50 "Bamboo Bomber", then the original 310, and then, I think, a 310C. Sky kept upgrading!
To my knowledge, the only 310 seen in the TV series was a 310B. A swept-tail 310D was used by Kirby Grant for promotional tours after the series ended. I've heard that might have been his own airplane. I even found a promotional photo of him on the wing of a C-320 Skyknight, with the "Flying Crown" and "Songbird" logos on it.
Wikipedia says the original
Songbird, a Cessna T-50 Bobcat owned by Paul Mantz, was grounded after Episode 39 due to structural wood rot. Googling a little further, an
article in an old Cessna T-50 type club newsletter quotes Kirby Grant as saying that two T-50s were used -- one was Mantz's, the other was Grant's own airplane. They were externally identical, except that Mantz's airplane was converted to Lycoming R-680 engines with spinners on the props, and Grant's had the original Jacobs engines without spinners. That article is slightly suspect, though, because it claims the interview with Grant took place in 1987; in fact he was killed in a car wreck in Florida in 1985.
Songbird II (N5348A), the second production 310B, was supplied by Cessna free of charge for the rest of the series after the T-50's retirement. Another 310B, N87832, was also used in a few episodes, but was wrecked in an accident. N5348A was wrecked in a fatal crash in 1962. That registration number is now on a C-320C.
Though the series was set in Arizona, it was filmed in the Southern California high desert, mostly at the old (now abandoned) Apple Valley Airport, on Highway 18 across the street from the Roy Rogers Inn.