71z but L28 engine, could someone tell me what I have?

[Namerow]

17 hours ago, kats said:

I=alphabet /ai/.

The coding system for the numerals makes sense.  However, what is the purpose of the letter? For example, the coding for an engine block in my possession is '2329N'.  The engine was removed from a Z produced in April 1972 (VIN 079701) and its number (101275) matches the number shown on the ID plate taken from the engine compartment. If I understand correctly, '2329' indicates 29-March-1972.  But what does the 'N' mean? 

Edited May 10 by Namerow

[Captain Obvious]

11 hours ago, Yarb said:

Consume more Beer!! 🍻

Hahaha!!   

[HS30-H]

8 hours ago, Namerow said:

The coding system for the numerals makes sense.  However, what is the purpose of the letter?

Casting batch identification.

They would be casting several batches a day, and each batch would be given its own identifying code letter for quality control/traceback purposes.