We are planning to go overland from Damascus to Tehran this summer. Just in the early stages of planning right now, so any advice greatly appreciated. We want to include Iraqi Kurdistan too. Any pointers on route and mode of transport? What is the public transport like? What's a reasonable amount of time to do this in? (I know we could take months or years, but realistically, we don't have that time right now!) Is travelling during Ramadan a big problem in these areas?
You should get your Iranian visa beforehand in Damascus or somewhere before that. Crossing from Syria to Iraq in the north is too dangerous. Go north to Turkey and head into Iraq, there will be no problem unless you possess an Arab passport. Then you can take transportation to the Iranian border.
Ramadan is a good duration to travel in Iran because the hotels, sights, restaurants and other tourist areas are pretty available. Fasting will not affect the foreign travelers and they can eat and drink but it is better not to do that in the public.