Header probably more important than the tractor. I had a massey 9435 and it was an excellent swather. 30' was about max I would want to run though. Reel drive is even marginal on 30 and would be way too weak on 36'. U2 pickup teeth on reel are next to useless. Newer macdons have a much, much nicer reel.
I wouldn't be scared of a massey 9635 for 1000 acres of canola.