Here are a few photos courtesy of Ian Corbett.
Also take a look at an article from Snowmobiler's Race & Rally from 1974/1975. A great article on the Corbetts.

Ian on the track at Eagle River in 1974

Kawartha World Cup 1974

Kawarth World Cup 1974

Ian, March 1974.

Here is a poster of Ian from the World Cup. This was produced by Sno-Jet and sent out to their dealer network.