The A4D is an example of their use to solve aerodynamic problems. An extensive trial and error program resulted in an interim pattern of vortex generators used on the A4D-1 and a different one on the A4D-2 and subsequent Skyhawks. Here is an example of a pattern that was evaluated and not adopted:
The actual pattern used on production A4D-1s were on the leading edge slat itself along with six on the fuselage, in this case ahead of the mid-fuselage break. (There are also two on the wingtip itself.)
Note that the barricade engagement fences have not yet been added to the slat as they would be on production A4D-1s.
The vortex generators on the fuselage were not always in a line vertically.
During production of the A4D-1, a different arrangement of vortex generators was developed for all subsequent Skyhawks. The ones on the fuselage were deleted, a different pattern (same number) was used on the leading edge slats and the wingtip, and a second row was added on the wing ahead of the ailerons. (Note the fences for barricade engagement on the leading edge slat.)
There are no kits of the A4D-1 as good as those of the A4D-2 (A-4B). However, the vortex generators are not the only difference between the -1 and A4D-2 (A-4B). A conversion from an A-4B also requires the removal of the inflight refueling probe and a "solid", i.e. non-ribbed rudder. The A4D-1 carried 150-gallon tanks early on as shown in the following picture. Note that every other vortex generator on the slat (which has been locked up) is edge-on to the camera, making them appear to be missing...
For completeness, here is an early A4D-1 cockpit:
And an early A4D-1 ejection seat:
Note that at least one A-4A was subsequently modified to have the additional row of vortex generators on the wing, while retaining the ones on the fuselage. Other A4D-1s are likely to have been modified to this configuration during Navy overhauls, as well as having the vortex generators on the fuselage deleted.
(The trough under the tailpipe is an experimental modification for IR suppression.)