Who was the European GT series world champion in the 1958-1957 years? or where can I find the answer?

Question

I'm looking for info about Rick Nielsen, European auto racing in the later 1950"s. Supposedly 2 years running world champion GT driver.

Answer 1

European Championship for GT cars
For years, the GT cars did not have a championship of their own. They provided full grids in WSC events but little else. But in 1972, Parallel to the ETCC, a GT trophy and later championship was organized. It turned out to be a Porsche affair with little attention from the press. After 1976, the championship was axed.

I don´t recall the name of Rick Nielsen in European Championship ... sorry