See second photo. I have 3- F-fittings available for the 1966 tripower.
The first F-fitting is the metal F-fitting, the middle is new F-fitting now available and the last fitting is this one you are looking at.
This is claimed to be the correct vent hose connector for the 66 Tripower. The connector has the OEM markings and part # 9784831. The quality is excellent. There are a pair of 3'8" posts pressed into the intake between the center and rear carbs. Hoses attach to the nylon connector. The connector points to the passenger side. Another 3/8" hose runs to the PCV valve in the valley pan. I also have two other connectors in the shopping cart that are shaped as an F-fitting that have been used on the 66 intake. The custom made F-fitting is white in color, without any markings, has the F-shape and is the center F-fitting in photo. Top F-fitting is made of metal and will last a lifetime, though it is more costly.
Also have a kit on the page to replace the rubber hose going to the the intake and PCV valve from the vent hose connector.