Here is an Ebay auction for a used Hipo 289 carburetor spacer used with PCV by Ebay member "eduardgonzale699" with a Buy-It-Now of $75.00:
Mustang Shelby Cougar Original Carburetor Spacer 289/302/351W/390/428 Cobra Jet...nice original hard to find 1 inch tall carburetor spacer... Fomoco brand...made of aluminum...
Mustang Shelby Cougar Original Carburetor Spacer 289/302/351W/390/428 Cobra Jet | eBay
-Fred-