Need help understanding date codes and sequence motor numbers

The real world answer is...........

There is NO pattern.

Here are some reasons why;

These cars were not built in VIN order.

The dates on the fender tags & broadcast sheets are SPDs (Scheduled Production Dates). This is the date they HOPED to build the car when the order was first entered into the system.

Actual build dates can be different by a day up to weeks, either earlier or later.

In addition to that, engine assemblies were completed elsewhere & shipped in to where the cars were assembled, transmissions also.

If they needed one of either with the correct part numbers for an imminent car build, the respective department could pull them & get them to the main line where they were mated together.

They were then stamped with either the cars partial VIN or full VIN depending on model year & time of year.

In your case they would have both been stamped with 2B 162797, same stamp set, bang-bang, one right after the other.

So........

The only real way for you to know the casting date & final assembly date on your block is if it actually surfaces so you can see what it says.

Best of luck with the search!

It is not hopeless, it does happen.