That is a overhead
valve motor. The 289 was stock in '65 and they ran some variation of that block, until 1995. Windsor is the name of the plant where the engine was originally built (or designed) as opposed to Cleveland, where the 'hot' big block style 351 originated.
Your car is an overhead
cam motor. It is 281 cubic inches, and the heads will not fit if you buy them. They have no cam in them to move the valves.
__________________
1997 Mustang GT "The Freak" - 13.80 @ 101.70, 2.07 60'
1995 Honda VFR750 - not much @ really fast (actual data pending.)
1964.5 Mustang 289
Rice Haters Club Member #13