Wrong VIN # Transmission From the Factory?
 

I just picked up a Kansas built 1969 L78 El Camino. It has the original engine. When I checked the trans number I found the VIN was not correct but what is strange is that everything else lined up. The date code P9B20 lines up perfectly with the build date of the car 03A. Also the VIN # stamped on the trans is very close to mine and is also a Kansas VIN #.

Any chance there was a mistake at the plant or a trans got swapped before it left the factory?

That happens. Here's my 1967 Corvette #350 with the transmission #349. The build date of the transmission matches the Warranty Plate.
Note that 1967 was the first year they used a separate gang for stamping the transmission.

Had a friend with a 64 vette like that. He went to ncrs they took points off for having the vin one off,so he restamped the trans and went through later w no deductions. He was foolish to do so but many cars have had one vin off like that, but normally it's one digit 49 to 50 is actually 2 digits,which means it wasn't stamped wrong it was just the car next to it on the line