As I understand it:
The Gran Premio Supercortemaggiore was run in 1953 at Merano (won by Fangio), on the old Monza road circuit in '54 (Hawthorn/Magioli) on the Monza road and track in '55 (Behra/Musso) and on the revised road circuit in '56 (Collins/Hawthorn). CORRECTION: it was the 1956 race that used the combined circuit.
There was a separate series of races at Monza called the Coppa Inter-Europa, run from 1949, in later years as a GT race as support for the Italian Grand Prix. There were often two Coppa Inter-Europa races, for smaller and larger cars. The last race for larger cars was in 1964 and the first race called the 1,000 km di Monza was in 1965 so a case could be made that the 1,000 km race replaced the Inter-Europa but it was a new event.
The results in the Wikipedia page linked to above seem to have the Coppa Inter-Europa winner from 1949 to 52, the Supercortemaggiore from '54-'56 and the Inter-Europa again from '57. The result it gives for 1953 refers, I think, to the Gran Premio dell'Autodromo, usually run as a single seater race and only in '53 for sports cars.
Edited by Roger Clark, 05 January 2014 - 10:31.