BRAINERD, MN - SEPTEMBER 17: Mark Donohue sits in the Porsche 917/10 ready to practise as team-mate George Follmer pulls into the pits of the Donnybrooke International Raceway at the Minneapolis Tribune Grand Prix, Round 6 of the Can Am Series held September 17, 1972 at Brainerd, Minnesota. (Photo by Alvis Upitis)