Rebuilt 318 Magnum. Is it a good deal?

You can verify the heads are EQ by casting number under valve cover area and stamping on the machined flat surface on each head. If it's good EQ heads cast in New Zealand, I would grab that in a heartbeat. Makes the whole package well worth a $1200 price tag.
The one thing I would do personally is have the heads checked by a trusted machine shop, paying close attention to the guides. A lot of those heads were sold without the guides being sized properly, so don't risk it. Have it checked.