You have to keep in mind that the "build date" on the cowl tag is NOT the date the car came off the line - it's the date (or, more accurately, the week) during which the raw body was welded together in the Body Shop, the first step in the Fisher Body plant, before the body ever got to the Fisher Paint Shop, the Fisher Trim Shop, or to Chevrolet. Under normal circumstances, it took about three days from that point before the body got to Chevrolet, and another day or so after that before the engine/chassis parts were pulled and went on the line, and another day before the car actually drove off the end of the line. That's why there's really nothing unusual about Chevrolet-installed parts being dated after the "build week" code on the cowl tag. For example, a 10B car could be in the Body Shop on Thursday or Friday and not have dated chassis components installed until the following Tuesday or Wednesday, which would be "10C" in Chevrolet terms.
On this particular car, the 6-month spread on the trans looks flaky, IMO.
MY396, in your case, if the trans was found to be bad, it wouldn't have been noticed until Roll Test, and Final Repair would have gotten another one from stock (not from another car) to replace it, and would have hand-stamped the VIN derivative, most likely one digit at a time (and could have stamped the last digit upside-down). If it's the same trans that was installed originally on the Engine Dress Line, the VIN derivative stamp would be identical to the one on the engine, as the same guy stamped both numbers with a gang-stamp right after the transmission was bolted to the engine.
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JohnZ
'69 Z28 Fathom Green
[This message has been edited by JohnZ (edited 12-13-2001).]