Chuck,
Thanks for forwarding his reply. Take a look and you will see that I said Chevrolet "factory produced" zero of them, meaning you couldn't order the Z-11 top half on a '62, nor did the factory assemble any and ship them out as done cars. (and that includes the factory aluminum B/FX Impalas, which came with the standard 2x4 engine). When the early Z-11 heads and intake set-up were first done (mid '62), the individual pieces could be gotten over the counter. The term "service package" implies the parts service system offered a "package", which would have it's own part number, as a kit which would include everything. They did that in April when the '63 cam, etc was put together as a package, and it had a package part number.
If a '62 Z-11 "package" would have been offered, it would have included the pistons as well. The Z-11 head has it's intake valve raised up .190"; just enough to nick the eyebrow. A lot of early heads were lost due to guys putting on the heads and intake without doing the work and using the right pistons.
And I agree: a set of "0-" pre-production casted heads would be worth quite a bit more than the "production" Z-11 heads.
Verne