AD or YH wheels.

[bcmiller]

Right Bill.  I have even heard of leftover MO engines used in place of DZs in early 69 Z28s.  That didn't happen either.

[KurtS]

Dates never mattered in the plant. They were just there to track & contain issues if necessary.
Mixed codes were possible. If they wrote the change notice as interchangeable and use/exhaust, then the line would be notified when the change was actually occurring and would know how to handle the last ones.
The broadcast sheet codes could lead/lag the actual change by a little bit, depending on how quickly they updated the system. There is evidence of this occurring. There are broadcast sheets with the new side terminal cables, but the cars had the top terminal cables.

[jdv69z]

So it is possible that one or a few Z's could have been built with a mix of AD and YH wheels? Not that it's really a big thing either way, but it is interesting. And also informative as to how the assembly plant worked.

[william]

This discussion belongs in the speculation section along with '69 Z/28s built with black standard grilles. Possible?  Maybe. How many are known to have been built that way? None.   

Since there is a dimensional difference in the wheels I question Engineering allowing it.

[X33RS]

I never say never but in the case of the wheels, with dimensional differences, I doubt they were mixed on one car.  My grandfather worked and retired at Fisher Body, and my father had a very close friend that retired from the Norwood plant.  Worked there from the 50's and into the mid 80's.  Even toured the plant before they closed and learned a lot of interesting things with inside knowledge.  Weird and unusual things did happen but a lot of this stuff is pretty cut and dry.  After all this time passed, and original untouched cars getting more scarce,  we may never know the answer to some questions. 
   My feeling, having a late December car with it's original wheels, I feel comfortable saying that at least the last couple weeks of December you likely had YH's.  Before that time I don't think it's out of the question to have either AD's or YH's on a 69 Z.  My opinion is that either would be acceptable.  How early on the transition appeared is the question.  With so few unrestored untouched cars from this time frame, especially non original owners, it may never be known.

[KurtS]

That is a question - what was in the original change notice? I never did any for a set like this, but since the offset and size are the same (same fit and function), they *could* have mixed them. The plant could handle the change however it was written. The big thing was to get the AD's out of there before the JL8's came down the line...

[X33RS]

I'm guessing Kurt, with that question, and the original question that started this thread, that we don't have a copy or draft of the change notice?  Are there any factory records at all about the wheels? 

[KurtS]

Not that I've seen.

[X33RS]

Thanks Kurt, I figured there probably wasn't but thought I'd ask anyway.

[william]

There is a copy of the engineering drawing for the AD wheel on page 318 of "Chevrolet By The Numbers 1965-1969."