Those are the later 340 pistons. The early ones only had two eyebrows. I'm not even gonna get into "what year" the break was, because everybody always argues, but that's what you have.
The chamber volume would have to be really small to get 11:1 out of one of those. The early style two relief piston .023 out of the hole and a FelPro 2003 gasket will just get over 11:1 with a 60cc chamber.