I've trawled the web and found a list of entries in the race programme for the 1960 Rhodesian Grand Prix which this car won. The engine size is shown as 1470cc.. These engines were widely used in South Africa and neighbouring countries, and the following year (1961) they complied with new F1 regulations and could take part in bona fide WC events.
I feel there must have been an Alfa tuning specialist in that part of the world. Doug Serrurier?
By the way, I realised today that Bob Chase once tried an Alfa 1900 engine in a Cooper T23 Formula 2 car, but its handling was awful, and he gave up on the idea.