Face it, the Intellivision controller sucks. Not many people care for a controller that has sixteen directions if it's wretchedly uncomfortable to use. I'm sure many people would sacrifice the precise directional control if they could use a stick of their own choosing.
There are a few problems with adapting the standard stick to the Intellivision. Fortunately, they all have easy solutions.
On the Intellivision console side of the schematics, the number refers to the controller port pin number on an Intellivision II or Sears Super Video Arcade, and the color in parentheses refers to the wire in an ordinary Intellivision.
You will notice that the +5VDC source is not carried by the controller connection. You will have to go inside the console, find a point to get it, and run a wire or something to the outside world. Ground is taken to be the metal shield, and +5VDC is referenced against it.
As an alternative to the 74266 Quad XNOR, you may use another 7400 Quad NAND, which is more likely to be available in your stash of extra parts. All four gates of the second 7400 plus the one gate left over from the first are used to construct an equivalent XNOR.
The last thing to construct is a Y-adapter to allow connection of the standard Intellivision controller so you can use its keypad functions. Simply connect the pins of the female D-sub you plug into the console jack to a male D-sub jack, pin 1 to 1, 2 to 2, etc.