The date is NOT the build date. It could be, but there is no way to know. It is the Scheduled Production Date - the date they HOPED to built the car when the order first entered the system.

Due to various reasons, the cars were not built in order by VIN.

The sheet you found has a B SN prefix. I see a 0 in the VON, not a 9?

I study 1970 Hamtramck cars / broadcast sheets for the most part, but cars from that plant were occasionaly built one after the other with a 15,000 spread between VIN numbers with no regard to the SPD at all.

As far as broadcast sheets ending up in the wrong cars goes.....

Once the trim shop had the seats built in the right color with the right pattern, that seat was delivered to the main line. The person there just grabbed the closest seat that matched what he needed & installed it, so the sheets in the seats do not always match.