Actually in that pic, that appears to be a rubber PCV grommet, which wouldn't necessarily be towards the front half of the valve cover if it were plumbed into the back of the carb,so possibly the covers were installed on the wrong sides. But you are right, the other cover probably has the
oil filler cap.
Also Lou, that breather requires uses a small basket filled with mesh wire that sits in a recess in the intake below the breather. The basket keep
oil from coming up and out of the breather. When you buy the breather you should buy the basket too.