The engine block pictured by Mike90 is the one I have sold to an American customer in 1998 while he was spending some time in Retromobile.
This block was originally for sale by a French spare parts dealer who had it from Mario Righini scrapyard. The new American owner, a classic car dealer in La Jolla, though it was a tipo 512 engine due to the flat 12 configuration of the engine. Finally he had been stupid enough to auction it at Christie's in 1999.
Everybody know that Alfa Rome never built the car but at the time I had heard that a complete engine exist as a two cylinder engine of the same type (a cut flat 12).
One or two years after (1999 or 2000) the same spare parts dealer had the complete but minus the carburetors, engine for sale at Retromobile. He asked 1 million French francs. The engine has been sold and he let me know the the new owner would intend to build the car. So any new would be appreciated.
With that being said, the picture of the engine on Righini website may be different from the one I had. I will try to find the pictures I had from the engine when it was home and will post them.