The plastic piece on the end of the air cleaner duct and valve was not available separately and never had a service part number assigned to it. It is part of the air cleaner duct and valve assembly, including the flex tube. You can see in bdennis's illustration that the angled-down adapter is stapled to the duct and the flex tube to it. The flex tube was permanently fastened directly to the air cleaner duct and valve in other applications. In 1974 Ford started transitioning to attaching the flex tube to the hard plastic duct that ran under the battery. The replacement costs were still objectable, especially to fleet owners. The replacement cost for a duct and valve assembly for D2ZZ-9A626-A (Q, R codes) and D2ZZ-9A626-B (F, H codes) was 26.35, the equivalent of $188.59 in 2023 dollars. Ford eventually released part numbers for a service flex tube
with lever-style clamps on both ends.