For the L67'*, there are enough in the pool for now. L27'* and L36'* need to send in 12 to get things started. You'll get a good matched set of 6 that way. And it'll leave some in the Pool. Chris said he'd post the pool numbers today after a count.
Remember, if your fuel injectors have a 3-5% spread from highest to lowest, some cylinders are running richer or leaner than the others. But the O2 is only looking at an average of the 6. If you had 6 O2 sensors, you wouldn't care.
By matching them more closely, you gain efficiency and power, and prevent potential KR issues on one or two cylinders when you're pushing the limits of pulley sizes or timing advance (NA).