Need help understanding date codes and sequence motor numbers

So I just spent over an hour on the Lost and Found page trying to find the original 340 and 4 speed for my 72' Dodge Demon.
Long shot I know BUT worth the try.

So as I am reading thru one 340 number after another I start to try to pattern the date codes
cast into the block and the 8 digit sequence code (last 8 of the cars vin) and I cannot for the life of me make any correlation between the two.

So my last 8 of the vin are 2B162797
What should be the date code of the engine I am looking for?
and how does it line up with the vin? How off can it be?
Car was built Sept 16th, 1971 ( according to fender data tag) but COULD it have come with a 1971 cast block and how early in the year did they produce the blocks before the body was made? The original owner I bought the car from told me years ago it had a 71' 340 steel crank motor new because it was such early production run. Anyone got info on that nugget of info?

Vin says Engine code is H - 340 single 4BBL 240 hp cast crank
Fender tag says E55- 340 4bbl 275hp steel crank


Thanks in advance!
Joe