Differences 9n,2n?

Hi! Just trying to educate myself. I just bought a '44 2n (thought it was a 9n) and am trying to get it working correctly. From what I've read I think I should have gotten an 8n (4spd), and other upgrades. But I haven't seen anything that differentiates a 9n from a 2n other than color. (I know some 2n's had no electrical for the war). It doesn't make sense that they would change the model number for nothing. So just what are the differences? Thx- Mike