Thanks for the leads, Ken!
As it turns out, it'd been so long since I disassembled this engine, I forgot what I'd put in marked cans on the shelf. Going thru them, I found a small tube that goes into the road draft hole at the back with a long bolt to fasten it. It reduces down to a hose fitting, so I guess it does require a PCV after all.
I think the tricky part of using this engine will be in how I'm going to attach an alternator. These early GM heads, as you know, weren't drilled for accessories.