Screw down breathers are required now at most tracks running events. That is why I mentioned it. They are also shorter going into the cover. Many places are making them. Morroso makes them and are usually hanging up on speed shop walls. They come with a rubber Oring seal, and washer. They are height adjustable and the nut locks on the inside. Some you can weld a threaded bung on.

as I said, I run an exhaust evac system, or sometimes just 2 breathers (screw on) on the front of the v/c myself