One thing I've learned is you can never underestimate what GM might have been doing.
But looking at the dates involved I would question that the intake of the original engine was defective and replaced with another then installed in the car.
Engines were not started at Tonawanda but were pressure and hot tested before being crated for delivery. The engine date and suffix ID was stamped about halfway through the assembly proceudre, ie., before the heads, intake, exhaust, etc. were installed. See
http://www.chevellestuff.com/tech/engine_assembly_order.htm
So if sometime between the engine being date stamped (Nov 22) and completion of testing (probably same or next day) if the intake was found defective would the engine be pulled and sit in repair rack for two weeks or would the defective intake be pulled and replaced right then by a maintenance/repair station?
Would the engine assembly process be like the Lucy & Ethel candy wrapping assembly line? Surely there must have been some repair stations set aside for minor problems. If no more intakes were available until Dec. 3rd, that'd mean no more engines could be built and shipped after Nov. 22 until intakes did become available on Dec. 3. I doubt that would be an acceptable policy.
Dec. 3, 1971 was a Friday. Did Tonowanda take a fresh batch of castings on that day and catch up on all the engines that needed them since Nov. 22? That would take some time at least to paint, install, pressure test and hot test before crating and shipping the following week.
It was stated the car was built the first week of December; I assume that was derived from a 12A body date. Nobody and no place I've found yet has defined what physical dates made up "A" week, or "B" week, or any other letter week. Looking at previous years & plants, there seems to be no consistency or standard for the dates of a given letter week. Why would a plant (or 2 plants) have, say, an "E" week in a given month when two different plants would have an "E" week the following month? My conclusion, different plants had different methods of defining the days/dates of a given letter week.
GM would have had the car in the system schedule to be built prior to or during the "A" week, whatever physical days "A" week might consist of, assuming they had all the componets on hand. Fisher didn't build the bodies not knowing if the final assembly line had their parts to complete the car and leave them sitting around the factory waiting for major components.
Bottom line, with a 1st week body date on the car, a Nov. 22 dated engine block, shipping, car assembly times, etc. a Dec. 3rd intake would not
likely have happened.
