Unique to the 1973 Mercury Cougar and Ford Mustang with 351 engines. This is a two piece ducting that connects to the air cleaner snorkel with a flex tube. Hard to find in this condition, the lower section has a metal tab that gets corrosion from the battery. Sold as a two piece set, Grade A will have undamaged mounting tabs. The Ford MPC specifies that this is only for the 351-2V and 351-CJ (351-4V) engines.
Ford part number D3ZF-9A624-A.