The Douglas Skyhawk is one of my favorite airplanes. I even wrote a book about it, Scooter!. When Airfix released a new 1/72nd scale kit of it two year ago, I devoted several posts to it. See http://tailspintopics.blogspot.com/2012/07/new-airfix-172-4b4p-modeling-notes.html
For an excellent built article of it by "Speedman" on Britmodeler, click HERE. This is a picture from that build:
Airfix had used the A4D-2 displayed on Intrepid as a basis for the kit, including the decals. Speedman decided to replicate that display, even to the point of adding red aileron-control-surface locks.
Neil Lowe posted a question about the Airfix kit on my post on A4D-1 vortex generators (HERE). He noted that there was a detail on the top of the fuselage between the canopy and the red anticollision beacon that is suggestive of the vent that is only present on the J52-powered A4D. I hadn't noticed it before. He also asked about the access panels in this area.
As far as I know, there is no vent in this area on the J65-powered A4Ds (I haven't seen any pictures of the top of the Intrepid A4D but I doubt that it has the vent). This is a picture of an early A4D-1 that depicts this area and the two access panels.
So for J65-powered A4Ds in general, this detail should be removed from Airfix kit. Whether or not you add the access panels is up to you.