Z heads? ARE THEY 360 OR 340?

Mrmopartech said
The Z head is a 3418915 casting number used on 70-71 360 motors with 1.88&1.60 valves and open chambers,I hope this solves the problem,mrmopartech

Very interesting to me as we pulled the motor from my 70 swinger Friday night. It to has Z on the heads. It is also Stamped with 2780930-340-5.
It also has 3B404335 on the rail which, I think makes it a 1973 motor. Am I correct?,also a bit confused.