It really is a shame that good kits of the Yorktown don't exist in the 1/700 scale, although I personally prefer the larger 1/350 scale. And a check at a couple of sites seems to indicate that it may now be difficult to find the Tamiya Enterprise CV-6 which seems to be discontinued.
Yorktown and Enterprise (CV-5 and CV-6) were both commissioned in the 30's and as sister ships were very similar, so much so that at one point prior to the begining of the war, Yorktown had a very large "Y" painted on her island so the pilots wouldn't land on the wrong ship when they were operating together. Saratoga had a large black strip on her funnel to differentiate her from Lexington, so don't feel so bad about having a hard time recognizing the differences, as for the most part they were not huge.
CV-7, Wasp, was essentially a "one -off" ship, as the Navy had to reduce her size and weight to stay within the limits of the Naval Treaties we'd signed. When it came time to build the CV-8, although there had been a lot of lessons learned and a new class was under development (the Essex Class) to save time and money, Hornet was essentially a "repeat" Yorktown class. However there were a lot of differences and improvements which would mean that while you can use a Hornet kit to make the Yorktown, to be accurate, it requires modifications. And as Gordon pointed out, to make the Enterprise at the time of the battle of Midway, from the Hornet, other modifications are required as well.
One of the things that is fascinating about ships (and this from a retired 30 year Army officer) is that unlike armor vehicles, which can be lined up in the motor pool and other than bumper numbers essentially be identical, not only vary one from another within a class, but change over time as well. So when you're depicting a ship during a particular battle, photos and research tend to be a very important part of the project.
A good example is Lexington, CV-2. For years a distinguishing feature of these ships was their 4 turrets with 8-inch guns. But they were removed from Lexington prior to Coral Sea, so the modeler building Lexington for this battle would have to take that into account.
As important a battle as Midway was, and given the unique factor that it was the only time all three Yorktown class ships fought together, you'd think that someone would do a better job in offering the modeling world the ability to accurately depict these great ships at that point in time.