anyone know what is the correct spacing between the fan and the rad?
I don’t know what engine you are running, but rule of thumb is the fan blades should be half inside the shroud.
I am running a 351c, and the fan is about half way out of the shroud, however I am not sure the shroud is correct,
What counts is the match between the fan and the shroud, not the gap between the fan and the radiator. The fan, if located correctly, creates a low pressure area behind the radiator. The shroud keeps air from coming around the sides.