A bolt!
Yup! Strange things you see used to plug a vacuum hole.
Hopefully the threads are still good.
You can remove that bolt and put your pcv hose there.
You’ll need a fitting to hook it up.
Parts stores have them. Sometimes plumbing sections in hardware stores have them.
Look here. Top row on the right is what you need.
https://www.classicindustries.com/sh...uum%20Fittings
What’s the big yellow cap covering on the top of the carb?
And what do you have for a breather on your valve cover?