Those aren't that old school ! Your breather is already in place, and I would bet there is a oil baffle under it. I won't swear to it but I would bet there is a knockout plug on the other valve cover with a oil baffle already under it. If that's the case ( and I bet it is) all you need is an pcv grommet and the pcv valve and of course your vacuum plumbing.

Holley Performance Products SB Chevy M/T Valve Covers - Polished*241-82