Monaci Bimotore 8C (1952): two engines from Fiat 500 C.
Two were built, only this is survived
Well, I thought it would take longer than that. It's good enough for the point, although the history of the car was a bit more complicated when I researched it. I found the marque originally when I saw it mentioned on the entry list for the Naples Grand Prix in 1952 (a race which is infamous amongst motor sport historians for its bizarre entries, not just that year but just about every year ). I found the puzzle picture but the website was in Italian, and that language is not my strong suit. What I have found out is that two cars were built, as you say, one in 1948 and one in 1952, the first with two Fiat 500 engines, and the later car, which I believe was the Naples GP entry, with two Fiat 1100 engines. (The race was held to Formula 2 regulations , 2-litres unsupercharged or 750cc supercharged, so I assume the engines were linered-down).
This puzzle car I reckon is the 1948 car, unless it is the 1952 car re-engined. To be honest, I don't know. Why, oh why, would an enthusiast go to all that trouble when it would have been simpler to fit a standard 1100 engine and go sports-car racing? You have to applaud him. The engine...