There have been a lot of cars built in recent years based on more modern Alfa Romeo engines, but made to look like a 1950s race car. Many come from Argentina. It doesn't look like any official works car to me, especially since it's LHD and the 6C3000 cars were RHD.
I think there's a good chance this is a recently-built recreation based on Alfa 1900 or even 2000 mechanicals.
I'd like to be wrong.
PS According to someone on an Alfa enthusiasts' site, it is a modern car made to look like a 1950s racer, and the engine is from a Montreal. The designer was Enrique Scalabroni.
