1966 GTO 421??

[Bobcat]

Since, I don't have time to recreate the three shifts and the out line of the Pontiac assembly line process. Let me Refer you to the GTOAA monthly magzine "THE LEDGEND". Which in 1993 Eric White did a complete series of approximately 8 issues, from January to December 1993. The series of articles were titled "Made In Pontiac" gives a nice general overview of the Pontiac assembly process in Pontiac. This will give an insight of the workings.
First, there were three shifts. With each shift having approximately 200 engines always on the hook. Each engine was tested then placed on one of two round tables and run for about 30 seconds with instruments. Reject and install. Good motors where hung up to besent down to plant 8. If a excessive run of bad motors or somthing happened, like an engineer needing an engine the line was NOT interuped for long. The plant was also shipping motors to other plants. and sometimes instead of a three day supply they could be as close as one to one. Unit to engine. There were approximately 500 bodies in the Fischer Body bank across the street. The plant wasn't as hung up on numbers as you are. Most of the other car company's only go by approximate date codes. But even Pontiac would pull out old stock that could have been stored several months. "House Rule was 30 - 90 days that the engine should be installed into a car.
Defective engines got into cars and where put into the "100%" or reliablity hut behind plant 9, that would fit six cars, and would have complete engine pulled and exchanged. The engines prior to 1968 were unit number NOT body VIN. numbers.
SO, NO THIS WOULD NOT DISRUPT THE ENTIRE LINE. Only a few cars in line and any car that was pulled for problems and placed in the reliablity hut. Pullys were installed down the line. Body's were dropped after the drive line, suspenion, wheels and tires where on the chassis.
Modern assembly, loads the craddle with all the pully's etc, under the already assembled unitized body. These where body and frame.
Computers are now used. Punch cards and typewriters in the dark ages.
Contact the GTOAA and get a copy of Eric White's series. Be informed. Some of the plants are giving tours, take one.