Chris,
What makes the 1959 model Bonniville special was that it was the first, of the many which followed with the same name. As it was basically a twin-carb Tiger 110 it was the only year when it had Triumph's famous nacelle. Personally I think that it was the best as it didn't suffer the later design problems of oil-in-the frame, vibration, etc. of later models.
Peter C.