I don't believe the timing marks are different. They are both offset. The 69 Z balancer has the pronounced 3 fingers that go from the center out without a ring around the edge. (Fingers stand out on the balancer where the pulley is bolted.) I don't think you could have bought an assembly line balancer over the counter. The NOS ones were the new versions like the 1970 LT-1's and up. Page 46 in Jerry's book is a good illustration. I can't post pictures if my life depended on it!
Sam