Not sure on the seat but as far as I know they were all the same metal "flip over" style seat. To the best of my knowledge the padded covers were an option/luxury. Also on the "live" pto, that was an add on made by the Sherman brothers who also made the Sherman transmission that was offered on the 8N.
I will narrow it down a little because I just thought of another difference that started in 1950, so there are actually 2 noticable differences between 49 and 50 one at the front and one at the back. I will take either one as the correct answer and give the other away when someone gets the right answer.