Yes, I know my air cleaner lid is not the correct one, not the factory original, but I haven't told anything because there are repros from the most common vendors, so I can get not the original but one that fits the car.
Well you'll need to look for a used original lid over time
Understand that there were only one nipple in the snorkel in the original car at some time, and later the other nipple in the lid. Yes, I also understood in maybe earlier versions, the larger hose went to the air pump air filter, but later to the other nipple in air cleaner. And also have clear that I don't have the oil cap with the breather to connect the hose between this and the nipple in the snorkel. That's clear to me now, and if I haven't mention is because i think they are easy finds, repros at least, and that's good enough for me since I don't have probably other options.
Looked through a bunch of pictures and it appears that both types of 6 cylinder systems with Thermactor used the air cleaner lids with two nipples. In cars with the Thermactor that used the hose to the Thermactor air filter the second nipple was capped and the other nipple was used for the breather connection
Did look at a dozen or so books focused on emission systems from the period as well as my pictures I can offer the following
There were two systems used For lack of a better term I'll refer to them as system A which connects the back fire valve to the engine air filter and System B where the same hose is attached to the Thermactor air filter cover/lid like found on 240 6 cylinders and 67 Shelby's
Looking at pictures of cars originally equipped with Thermactor built at San Jose and I see System B on very early cars and those in the 6R18xxxx though 6R19xxxxx period. I found System A style installed on cars in the 6R12xxxx-6R16xxxx and (similar to your car) in very late cars around 6R226xxx
System A (for our discussion purposes)
Showing hose going around and to the engine air filter lid
System B (for our discussion purposes)
No hose around back of the engine but instead to the Thermactor air filter nipple
That been said, I think until here I'm clear.!
So, what's next now..? How to determinate which valve do I need..?
Would go with the three port for your usage and time period Its likely a used one will have worn finishes (gold dye for the main body and zinc dichromate for the top cover). There are new ones out there but can cost a bit but its cheaper compare getting the plating done/correct. Of course allot of NOS ones are in poor condition after all these years so check condition first. That is likely why those pieces are in the box and not installed on a show car
And something else to be on the look out for
The smog pump valve cover
