VIN number does show the order they came down the assembly line
This is a common myth actually. All of the plants built cars out of sequence for whatever reason, it is something I am researching in-depth for 1970 right now.
Until then, think about this.....
This thread is about a 1974 Challenger, they were all built at Hamtramck. Hamtramck had two assembly lines. So, IF (big if) the cars were built sequentially by VIN, odd number cars would have to come from one line, while even numbered cars came from the other. They would also have to time each build EXACTLY so one line did not get ahead of the other to have the cars leave sequentially.
Did they do it that way? Nope. It would have slowed the lines down to a crawl trying to micro-manage it to that degree.
The actual broadcast sheet sequence numbers have a whole lot more to do with the actual build sequence than the VIN does. As an example, broadcast sheet # 1000001 was printed for BH23G0B100052.
So, right there, for 1970, Hamtramck started 51 VINs behind.
It is common for cars 6000 to 7000 VIN numbers apart to have been one behind the other on the assembly line.
Research as always, continues............