Leo, so your a tall guy too, you have me by 1 inch.
On a recent trip to Paris, I was able to book an exit row on the return when I booked the ticket. On the outbound, I was told that it was blocked and could only be assigned on the day of departure.
I was in the E concourse 1 week before the trip and stopped by the counter when I saw a Red Coat. I asked for help and she went to unblock the row so we could get our seats. When she did this, she found that some one else had done the same thing and the seats were already booked even though they showed as blocked in the system. She then looked in the system and booked me a later AF flight in the 1st bulkhead row on an Airbus 340. I think those are the best seats on the plane as the wall doesn't come straight down.
I have been able to book exit rows on international flights 90% of the time way in advance.
Good Luck