Identifying stampings on a big block

[dlrogers]

 
Hi all
I have some block stampings on the 383's block that I wouldn't mind some help with please.
First, on the port side under the spark plugs is 90 28 056. (The '0's may be a dot).
Then on both port and starboard banks are larger castings reading 2468130.8 (on both sides).
Towards the front on the starboard bank is a clock face (with 10 instead of 12 marks) and an arrow pointing to where the 3 O'Clock position would be.
Finally, on the same side are two letters, N and O (or D) with an arrow like that in the clock face pointing towards the N.
I have gone through my manuals but these stampings are not described in them - any help would be appreciated.
Cheers
David

[Chryco Psycho]

the block was a 59-71 block by the casting #
 the date Has to be wrong 9/28/66 would be my guess so it was cast sept 28 66
 the N is night shift 

[dlrogers]

OK, thanks for that CP - always good to learn something new.
Cheers
David