Engine Identification - need help

Good evening,
I think a found a year correct engine for my 69 Barracuda. I compared all numbers (Heads, Block, Intake etc.) but here is what confuses me:

The stamped number on the block I want to buy shows PM318R 26142457 (which I believe should have been built on 23. Sep 1968 - would theoretically suit my car built-in 07. Jan1969

The Mopar parts Catalog for 69 gives an example for all 68 engines
Date code 2187 - 24. July 1968

If I put the number 2187 in the maxwedge calculator I get
Date code 2187 - 24. July 1967

So what is now correct - or am I just on the wrong path? Here are screenshots:

Thanks, Wolfgang

View attachment 1715421629

View attachment 1715421631


The last 8 digits on the block under the left side head are for date code and sequential number of engines built that day....

How to ID a Small Block Engine Block: