D1OE-9425-AA would be the part number.
D: decade, just as telicoman stated
1: year
O: other application, truck would be T, Z Mustang, etc.
E: parts group or engineering component (engine)
9425: actual part number within the parts group
AA: revision or engineering version; A would be first gen, B second, etc.
Casting dates are a little less obvious. In this case, the casting date was "1E18". Translates out to:
1: 1971
E: 5th letter of the alphabet, 5th month of the year is May
18: 18th day of that month
18 May, 1971.
I spend way too much time reading on the internet.
http://www.mustangtek.com/FordDecode.html#Table21