Just installed a Goodmark cowl hood on a 72 and we want to use an air cleaner housing to take advantage of the cowl induction. What will work?

Jim… Welcome to T/C!
I too have just installed a new Goodmark cowl hood on my 73 Z28. I picked up a dual snorkel that was used on an early 2nd gen. Camaro (this was what I was told) with the cowl ring and rubber gasket to fit up into the cut out cowl area. There are 2 kinds of rings, a tall and a short height; the tall unit is used in a 2nd gen., and the short on a 1st gen. All these parts are available from the after market parts houses, but will cost. I found mine in the want-adds here on T/C.
Hope this helps.
Mark (A.K.A. Z28 Mark)
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The tall and short extensions are also used in first generation. 302 used the short one, and 350 used the long one. B/B used no ring.