Murphy,
Do us a favor and fix your Equipment list to say KUBOTA not Kabota - many people seem think that it has the ol "A" for the second letter.
On the oil note -
That is a 40+ year old tractor - and being in the colder seasons up there in Nova Scotia I would highly suggest a oil that will perform well when starting in the cold.
20 weight might have been fine in a warmer climate - but if it was mine I would run a 10w30 or even a 5w40 - those cold starts are helped by the less viscous oil. I bet you can find a Rotella T6 up there?