That's a good question. It's at least a '69 because of the high-mounted side marker lights. I've wondered about how to ID the years other than this.

Also what year did the rear fender change to be like the front one? In the video you posted the rear fender is lower than the front. But many times it appears like this:
http://imcdb.org/vehicle_7019-Ford-Bronco-1970.html

When did it change from this?
http://imcdb.org/vehicle_502045-Ford-Bronco-1970.html