Air conditioning was available on all SS396 engines except the solid lifter variety.
I'm by no means an expert on 67's but I would guess the 325 HP version came with an enclosed air cleaner assembly with air snout(s). The higher horsepower cars would have come with an open air element.
Except for the possibly rare 375hp L78 which doesn't show up in standard 67 Chevelle literature, both the base 325hp and L34 350hp 396 engines came with hydraulic lifter camshafts and both could be had w/air conditioning according to Chevrolet options.
The base 325hp offered the snorkle type air cleaner while the 350hp version got the open element type.
Just to add to the above, right below the air cleaner on a 325 HP model should be a Quadrajet carb and on the 350 HP model will be a Holley (I believe it is a 585CFM) Maybe that is why the difference in air cleaner style as Dale pointed out???
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