The intake is an Edelbrock crossram. Edelbrock part # STR-11. It was available from the AMC dealer with an AMC part #, or direct from Edelbrock without an AMC part #. They were standard on the SS/AMX. They've been discontinued for about 30 years. They pop up on eBay once in a while, usually run between $2500 and 3500 depending if they have carbs and linkages.
Good only for very high RPM engines (drag cars), probably wouldn't work well on the street.
Here's an old ad for one.
http://www.amx-perience.com/classifieds/showproduct.php?product=229&sort=1&cat=all&page=37
Bob
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