21 June 2014: I added a comment on the detail on the upper fuselage between the canopy and the dorsal fin here: http://tailspintopics.blogspot.com/2014/06/more-modeling-notes-on-172nd-airfix-4b.html
21 November 2012: I added some detail on the landing gear sponson features here: http://tailspintopics.blogspot.com/2012/11/the-dirty-underside-of-a4d.html
15 September 2012: I forget that you might have gotten here by a web search or reference link and so might not have scrolled through the blog and seen the other Skyhawk stuff:
Nose Shape: http://tailspintopics.blogspot.com/2012/11/airfix-172-a4d-2-overall-size-and-shape.html
A4D-1 Rudder http://tailspintopics.blogspot.com/2012/08/a4d-1-rudder-development.html
Fuel Tanks http://tailspintopics.blogspot.com/2012/07/douglas-low-drag-external-fuel-tanks.html
1/48th Cockpit http://tailspintopics.blogspot.com/2012/09/fitting-in.html
7 August 2012: One point that I might not have made clear is that the external configuration of the J65-powered Skyhawks changed over time as product improvements were incorporated at overhaul. Airframe change dates aren't much help because it might take a few years before an airplane went into overhaul after a modification was approved. The A4D-1 in the New England Air Museum is an example.
3 August 2012: Thanks to Peter Collins, we now know the difference between the early and late oil vent on the right side of the J65-powered A4Ds.
I also added some information on the early and late wing tip lights.
2 August 2012: Added detail on differences
1 August 2012: I don't know if it's represented on the kit, but the A4D-1 and -2 had a small hole in the nose for avionics cooling:
The Scooter is one of my favorite airplanes so I was particularly pleased when Airfix issued a new kit of it in my scale.
Picture from the Hannants web site
For one of the build posts, see Drewe Manton's web site http://drewemanton.com/models/2012-07-27-a4b-800s/a4b-build-800s/vma324_a4b.html
Airfix based its new Skyhawk kit (it also produced a much simpler and not very accurate A4D-1 kit decades ago) on the A-4B displayed on Intrepid, which is now a floating museum docked on the Hudson at New York City. (See http://myaviation.net/?pid=02024117.) It therefore represents one that has been through rework and modification several times.
For example, here are some differences annotated on a picture published by "Ajay" as part of his build post here: http://z15.invisionfree.com/72nd_Aircraft/index.php?showtopic=2286&st=0
The kit also has the radar altimeter fairing under the left wing tip. This was added during A4D-2N production and retrofitted to some A4D-2s, including the one on the Intrepid. However, it may have to be removed depending on the specific A4D-2 being represented. For this and some other details on the differences between the A4D-2 (A-4B) and A4D-2N (A-4C), see http://tailspintopics.blogspot.com/2010/07/a4d-skyhawk.html. Note that the A4D-2N (A-4C) had a nine-inch longer nose to accommodate a terrain avoidance radar.
The major omission is the oil vent port on the left side of the fuselage. It was a significant feature in no small part because of the oil streak emanating from it.
Cropped from Peter Roan picture HERE
The missing upper rectangular openings just aft of the fuselage break (these provided access to the bolts that attached the aft fuselage to the mid fuselage) could be represented with paint or a decal for simplicity of construction...
I don't know whether the blade antenna aft of the canopy in the kit and on the Intrepid Skyhawk is representative of a later version or not, but the early antenna was clearly different:
The kit has a representation of a later version of the Douglas ejection seat, the main external difference being the addition of a vertical slot/channel in the headrest for the "head knocker" used to arm the later seat. It had better ejection performance and was introduced with the A4D-2N (A-4C) in early 1960. It was retrofitted to A4D-1s and 2s.
Another picture of the early headrest:
Note: The blade antenna normally mounted behind the canopy was installed under the nose of this aircraft.
The external wing tanks may be undersized and according to the pictures, have a constant cross section where they should be bulged. See http://tailspintopics.blogspot.com/2012/07/douglas-low-drag-external-fuel-tanks.html for more on the Skyhawk tanks, sources for accurate tanks, and a link to Douglas external tanks drawings.
There were early and later main landing gear wheel hubs. Some A-4s had the early hubs through at least through 1970. The kit reportedly has the early hubs.
For a description of the early angle of attack indication to the LSO, see http://thanlont.blogspot.com/2012/04/night-carrier-landings-in-beginning.html