Some more info from the vendors of this car 9in what I suspect is Google Translate English!):
QUOTE
Although this Fiat Topolino started life in 1952 as a standard saloon, she very quickly (in 1955) was converted by Macchi from Varese into this aerodynamic sportscar to participate at the Coppa D'Oro delle Dolomite in Apart from the drastic morphological modification also the engine (4 cylinder 600 cc) was tuned and upgraded with a nice period Abarth twin carburettor manifold and 2 Solex carburettors.
UNQUOTE