Disagree, but only with the "B" part of your post. The 383 Sixpack hasn't been available for years. And because they were never a factory option, I think they are rarer than the small block. There is just much less demand for the 383 Sixpack.
I have a 440 Sixpack intake that I'm not using, simply because of the price of carbs.
A Sixpack center carb is more money than a 1050 dominator.