Pin size of the top link on the tractor side is 3/4" and, as you stated, 1" on the implement side. Seems to be pretty standard for this size tractor as my 50 year old JD 2020 has the same size pins on the top link. Lift arms pins are the normal CAT II 1 1/8". Guess this keeps you installing the top link in the same direction all the time.