Hi Dave,
I watched the Rocketeer recently as well. Nice “get-lost-in-the-story” adventure.
As to the Gee Bee (Z Model), the replica used by Disney in the movie was purchased from Bill Turner in the USA. It’s not quite accurate – longer fuselage (by two feet) and wings (by 3 feet) and less powerful engine (by 85 HP). It was built in the late 70’s and now sits in a museum in Santa Monica, California. (info pulled from a bunch of websites)
For the crash, it seems most likely that a mock-up was used, as I’ve read a number of references in movie blooper sites to a cable pulling the plane being visible in the movie just before the crash. Will have to watch more closely next time.
Cheers,
Zoomie