Hmm, how can I explain this. You have a later engine, but the earlier ones had a threaded heater core fitting in the rear plate below the oil filter pedestal with a hex and nipple the same size and shape as the PCV valve on your manifold. Same thread pitch too. Yours is missing the plastic cap which allows a 5/16" hose to slip onto it. My cap was broken so I pulled it off, found a piece of heater core hose that fit perfectly on the nipple, and it just so happened to fit snugly on the hex part of an FV266. I decided to use a couple of zip ties around the hose on the hex part because they're cheaper than hose clamps and I have a nice zip tie tool to snug them up really well. I didn't want any air leaks. I also added one clamp on the nipple part of the PCV fitting just to keep it on there better. Note: I could have used a threaded heater core fitting if I needed to.
I've heard of using a caravan PCV valve, but I've found the FV266 to be perfect for carbs ranging from stock up to a 600 Holley (adapted to a stock separate runner intake manifold with an adapter plate). I've also been able to use FV333 on Edelbrock carbs on Camden superchargers. I just installed one on Saturday.
Nikki carbs do have a carb bowl vent that needs to be hooked up, so I assume your setup will work ok as you described it.
On my '79-'80 manifold, I didn't even bother with an ACV cover plate. I added an NPT pipe plug to the big hole and a screw to the small hole. Easy and free.
I haven't tried this manifold yet. I'm sure it will flow better than an FB manifold just comparing the differences. Visually it simply looks better.