See second photo. I had 3- F-fittings available for the 1966 tripower, as shown. I no longer sell the centered pictured F-fitting. I sell the top photo metal F-fitting and the lower Nylon hose fitting as shown here.
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 one other connector in the shopping cart that is shaped as an F-fitting that have been used on the 66 intake, shown in photo. Top photo with 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.