Here is an Ebay auction for a used Hipo air cleaner assembly by Ebay member "beamergirl37" with a starting bid of $375.00:
1965 Mustang Shelby 289 Hipo Used Air Cleaner 5A Date Code. Condition is Used. The top is just ok but not to bad for used please look at pics e-mail me any questions Thanks Richard upstairs
https://www.ebay.com/itm/1965-Musta…NcAAOSwjjdeJxxH
-Fred-
This air cleaner base is one without the nipple for a closed emission system where a hose runs from the nipple to the oil filler cap. All 65, 66 and 67 Shelbys need the nipple. A lot of other Hipo 289's do not need the nipple unless they are California cars.
-Fred-