Had the rather unusual experience of seeing the Land of the Giants Pilot episode. Unusual in that wouldn't expect that syndication from an outfit like MeTV. The first episode aired multiple times on the SyFy channel and was the showed the network production version. Never the pilot.
The pilot had a cold open, Joseph's Mullendore's unused title score, and borrowed John Williams Music from Lost in Space for much of the episode. The odd slow way the giants talked in early episodes was removed. Kurt Kasznar was listed as part of the cast but without "special guest star". It closed with Joseph Mullendore's unused end credits. Think but not sure that i might have had a different ending portraying Fitzhugh in a better light than usual..All in all an interesting experience plot wise and musically. Missed the production episode music.
You're talking about "The Crash", right? That had an original Williams score. May have borrowed from his LOST IN SPACE too, of course (I don't know, don't have the boxed set with the liner notes -- only the old Irwin Allen box). It's been many years since I saw the episode, so I can't remember what the ratio is between original score and borrowed material.