Gull wings a 300SL roadsters are such low volume cars that Daimler has the data cards and the names of every single first owner. if it was the former presidents car ,his name will be in Daimlers records. This story will no doubt unfold.
There is something fishy about the chev engine . If it was installed after the revolution it could only have been a 265 cu. in 1956 or 1957 engine but the distributor is post 1958 type with adjustable point door and the water neck is a 1964 item. None of these parts would have been used to keep a sports car running IF they were available, but were precious bits in big demand to keep a car running. Most cars were appropriated by the Cuban state and belong to the people . private cars being very few and far between. a running engine woul have been scored decades ago to keep another running instead of a lada Diesel like so many of those crap heaps in Cuba run.
The maserati would be the pick of the bunch if this is real and not some European restorers stash . The Gull wing can be restored from a chassis number ...
thats the 300's chassis you can see in this pic.
http://www.carsthatmatter.com/media/photos/2010/04/18/SSM11804.JPG