Strange 318 Block

mchartier105 said
Not a warranty block, it has numbers stamped in both places, I read "AC202" on the vin stamp and "OM318 04289587" on the driver side under the head.
View attachment 1715319370 View attachment 1715319371

Little bit of Decoding here:

OM318 04289587

O = 8-78 (date, built August 1978,) wonder if the cast number is a 78 instead of 79 ?
M = Built at Mound Road Plant
318 = Self Explanitory
04289587 = Have not figured this number out yet.